Diphtheria is a serious disease that can cause death through airway obstruction, heart failure, paralysis of the muscles used for swallowing and pneumonia. It is caused by the bacterium Corynebacterium diphtheriae, which produces toxins that cause cell death both at the site of infection and elsewhere in the body.
Diphtheria usually begins with a sore throat, slight fever, and swollen neck. Most commonly, bacteria multiply in the throat, where a grayish membrane forms. This membrane can choke the person. Sometimes, the membrane forms in the nose, on the skin, or other parts of the body. The bacteria can release a toxin that spreads through the bloodstream and may cause muscle paralysis, heart and kidney failure, and death. Approximately 5% of people who develop diphtheria (500 out of every 10,000) die from the disease and many more suffer permanent damage.
In the 1920s, before the diphtheria vaccine, there were 100,000 to 200,000 reported cases in the United States each year. Because of the high level of immunization, only about one case of diphtheria each year in the United States. However, in areas where the immunization rate has fallen (such as Eastern Europe and the Russian Federation), tens of thousands of people suffered from diphtheria in recent years. The bacterium is still here—even though we do not see many cases. Our children are protected by being immunized and by everyone else being immunized too.
The diphtheria toxoid (inactivated toxin) vaccine offers the greatest protection against this disease. The fully immunized person who is exposed can become a carrier of the bacterium but may only develop a mild case, or may not get sick at all. But if not fully vaccinated, the risk of getting severely ill is 30 times higher.
Haemophilus influenzae type b (Hib) is a bacterium that can infect the outer lining of the brain causing meningitis. Hib is transmitted from person to person through mucus droplets that are spread by coughing or sneezing. Invasive Hib disease occurs most often at three months to three years of age, peaking at six to seven months of age. The disease is uncommon after age five years.
Hib can cause a wide variety of serious infections, including pneumonia, severe throat swelling that makes breathing difficult (epiglottitis), and infections of blood, bones, joints, and the covering of the heart. Complications of Hib meningitis include blindness, deafness, mental retardation, learning disabilities, and death. About 5% of children (500 out of every 10,000) with Hib meningitis die despite antibiotic treatment.
Hepatitis A infection is caused by the hepatitis A virus (HAV).
When infected by hepatitis A virus, adolescents and adults are more likely than young children to develop signs and symptoms of disease, including fever, weakness, nausea, abdominal pain, dark urine, and yellow eyes and skin, and are more likely to experience severe disease.
Symptoms usually last less than two months, but 10% to 15% of those infected will have prolonged or relapsing disease lasting up to six months. Unlike hepatitis B and C, chronic hepatitis A disease does not occur. Unfortunately, each year in the U.S. 125,000 to 200,000 people become sick with hepatitis A. In the US, 70 to 100 people die― mostly those with underlying liver disease.
Most hepatitis A disease occurs in community-wide outbreaks. This virus is most commonly spread in stool, although it can be spread through contact with infected blood. Infection is transmitted from person to person in households and extended family settings. Outbreaks sometimes occur when many people have eaten from the same hepatitis A-infected food source but almost half of people have no identified risk factor. Infected people are most likely to spread hepatitis A virus during the two-week period before they know they are infected. Since most infected pre-school children show no symptoms of hepatitis A infection, they often unknowingly spread the hepatitis A virus to others.
Prior to the introduction of hepatitis A vaccine, about one-third of the hepatitis A cases in the U.S. occurred in children 5 to 14 years of age. The lowest rate of infection was in adults more than 40 years old. The rates of infection and disease were much greater in some areas of the country than others.
Hepatitis B virus (HBV) is transmitted from one person to another through blood and body fluids, and primarily infects the liver. In the United States, it is most commonly spread through sexual contact or injection drug use. Health care workers and others exposed to infected blood or body fluids are also at high risk for infection. Worldwide, it is most commonly spread to infants by their infected mothers.
Approximately 30% of those who become infected with HBV have no known risk factors.
More than half of those infected with the disease show no signs or symptoms, although they may become chronic carriers of the disease and may develop liver disease or liver cancer later in life (usually by age 40). Symptoms of HBV infection vary and may include loss of appetite, fatigue, nausea, and jaundice (yellow eyes and skin), joint pain, and skin rashes.
Worldwide, over 350 million people have chronic HBV infection, and approximately 1 million HBV patients die annually. An estimated 1.25 million people in the U.S. have chronic HBV infection. Each year, approximately 4,000 to 5,000 children are infected with HBV in the United States. The younger the patient is when the disease is acquired, the more likely it is that he or she will develop chronic liver disease or liver cancer.
Approximately 90% of infants who are infected from their mothers at birth, and between 30 and 50% of those infected before age five, become chronic HBV carriers, while people who are newly infected as adults have only a 6 to 10% risk of chronic infection. For these reasons, hepatitis B immunizations are recommended for routine administration at birth. There are specific protocols to identify infected expectant mothers, for managing children born to infected mothers, and to manage children born to mothers with unknown HBV infection status.
Human papillomaviruses (HPVs) are a group of more than 120 different viruses. Some are acquired by intimate sexual contact.
Approximately 40 HPV types are primarily sexually transmitted from person to person (for example, genital-genital contact, oral-genital contact and sexual intercourse), infecting the oral, anal or genital areas of both men and women. Genital HPV infections are very common: acquisition shortly after starting to have sex occurs commonly. One quarter of females 15-19 years of age and 45% of those who are 20-24 years of age have evidence of genital HPV infection. By 50 years of age, 70-80% of women and a similar percentage of men will have acquired genital HPV infection.
Most genital HPV infections cause no symptoms and are cleared by the immune system within a few weeks or months. Thus, the vast majority of people recover from genital HPV infection uneventfully. However, some people develop persistent HPV infection, some of which can lead to genital warts and others can cause cancers:
- Types 16 and 18 and others, known collectively as “high-risk” HPV types, may cause abnormal Pap tests and cervical cancer in women. Together types 16 and 18 cause approximately 70% of the cases of cervical cancer in the United States. Although there are a number of other risk factors for cervical cancer, being infected with a “high-risk” type HPV appears to be necessary to develop cervical cancer.
- In both men and women, “high-risk” HPV infections are also thought to cause 85% of anal cancers, 50% of other anogenital cancers, 20% of cancers of the throat and mouth and 10% of cancers of the larynx (voice box) and esophagus.
- HPV types 6 and 11 may cause genital warts. These two types of HPV are responsible for more than 90% of genital warts. These types may also spread from mother to infant during pregnancy or delivery and rarely can cause warts in the upper respiratory tract (throat, larynx) of the child.
Influenza viruses are grouped into 3 major types (A, B, and C), and strains are further divided into multiple subtypes depending on the source of the virus and the types of proteins on the outside of the virus particle.
Although influenza B causes many children to be absent from school, influenza A viruses cause much of the severe illness during epidemics. All influenza viruses quickly change as people become immune to the strains circulating in the population so that immunity acquired one year will only partially protect for subsequent outbreaks.
Influenza A viruses also have a remarkable potential for variation, mutating rapidly and also by being able to mix genetic material with influenza viruses from other species of birds and animals.
Influenza viruses can affect anyone, but rates of infection are highest among children. Serious illnesses and death also occur in all age groups but rates are greatest in persons over the age of 65 years and those who have chronic health problems. Epidemics of influenza occur during the winter months nearly every year but the peak of influenza epidemics can occur as late as April or May and is not predictable from year to year. Influenza is spread through coughing and sneezing, and is highly contagious, especially in childcare centers, schools, and nursing homes.
Uncomplicated influenza generally comes on suddenly, and symptoms include muscle aches, fever, chills, headache, cough, and runny nose; it lasts for 3-7 days although cough can persist for about 2 weeks. The respiratory illnesses caused by influenza viruses are clinically difficult to distinguish from the illnesses caused by other respiratory infections. Young infants may have symptoms that mimic invasive bacterial infections with high fevers and fussiness, leading to hospitalization. Although most young children who are hospitalized with influenza virus infections are only in the hospital for a few days, some require treatment in an intensive care unit. The majority of children who are hospitalized for influenza infection are less than 5 years of age and a quarter of them are less than 6 months old.
Influenza viruses can cause viral pneumonia, can make underlying medical conditions worse, and can lead to bacterial pneumonia, sinusitis and ear infections. Influenza virus infections have also been associated with inflammation of the heart and, brain swelling with liver failure.
On average, influenza virus infections cause approximately 36,000 deaths and 148,000 hospitalizations each year in the United States. More than 90% of influenza-related deaths are in people aged 65 years or older. Although influenza-related deaths are much less common in children than the elderly, fatal cases have been increasingly recognized.
An influenza pandemic can occur when a new influenza A virus appears against which the human population has no immunity and when the new virus can spread from person to person. This can result in several, and simultaneous epidemics around the world. These virus strains may result from exchange of gene segments between human and avian or swine influenza viruses or from direct transmission of nonhuman viruses to humans.
The severity of pandemics has varied substantially in the past. Depending on the virulence of the new virus—the degree of disease severity it causes—the numbers of deaths, hospitalizations, work that cannot be performed, and school absenteeism can differ a great deal from pandemic to pandemic.
In 2009 a new influenza virus containing genetic information from swine, avian and human influenza viruses emerged called pH1N1 2009, and was the predominant strain that circulated in the 2009/2010 inluenza season. While not as severe during the first season as had been feared, this strain caused a disproportinate amount of illness and deaths in children, pregnant women and among those with underlying health problems such as asthma and obesity. The seasonal influenza vaccine for 2010/2011 will include this strain.
Japanese encephalitis (JE) is a mosquito-borne disease due to a virus similar to the virus that causes yellow fever. It occurs throughout most of Asia and parts of the Western Pacific. Only a small fraction of people infected with JEV develop encephalitis but it is estimated that there are 35,000-50,000 cases each year. Of those who develop encephalitis as many as 20-30% will die, and about half (50%) of the survivors will have permanent brain damage. In areas where infection is endemic, almost everyone has been infected by 15 years of age.
JE occurs primarily in rural areas where pigs are intensively raised, particularly in regions with rice production. JE in pigs does not cause illness but pregnant sows that are infected often have still births so farmers immunize sows. JE is spread by mosquitoes which breed in pools of water: a single rice paddy, for example, can generate about 30,000 mosquitoes per day.
During the first half of the 20th century, JE occurred primarily in Japan, Korea, Taiwan and China. Japan has greatly reduced JE as a result of widespread immunization of children and the protection of herds of pigs. Vaccination has also reduced JE in China. In recent decades, however, JE has spread to Southeast Asia, India, Bangladesh, Sri Lanka, Nepal, Saipan and Australia. The reasons for the spread are not certain but scientists think it may be due to increased pig farming near rural rice paddies in these areas, or the virus may be spread by migrating birds and wind-blown mosquitoes.
In endemic areas, JE infection occurs primarily among children. However, travelers of all ages have become infected with JE. The military has estimated that among the unimmunized between one and two people in 100,000 per week is infected with JEV. Scandinavian tourists to these regions have been estimated to be infected at a rate of one in 275,000 with half developing encephalitis. The risk for travelers acquiring JE infection depends on the season of travel, destination (rural areas being much higher risk than urban areas), duration of stay, and likelihood of mosquito exposure (dusk and night time are the preferred times for biting mosquitoes).
Lyme disease is caused by infection with Borrelia burgdorferi, a spiral-shaped (spirochetal) bacterium carried by deer ticks and western black-legged ticks. The ticks are often infected by feeding on the blood of the white-footed mouse, the white-tailed deer, and various species of birds, though these animals do not spread the disease to humans.
Most (80% to 90%) of people infected with Lyme disease develop one or more red, slowly expanding “bulls-eye” skin rashes at the tick bite sites (these are called erythema migrans), often accompanied by fatigue, fever, headache, stiff neck, muscle aches, and joint pain.
If diagnosed early, Lyme disease can be treated successfully with antibiotics. If the disease is left untreated, some people will develop more serious health problems such as arthritis, problems with the nervous system, pain in the large joints, and rarely, heart problems.
Lyme disease was first recognized in the United States in 1975. The number of annually reported cases of Lyme disease in the U.S. has increased approximately 25-fold since national surveillance began in 1982; during 1993-1997, a mean of 12,451 cases annually were reported by states to the CDC, and the incidence is increasing. The disease is mostly found in the northeastern, mid-Atlantic, and upper north-central regions of the U.S., and in several areas in northwestern California. Lyme disease is the most common vector-borne (spread from one host to another through a carrier such as a mosquito, fly, louse, or tick) disease in the U.S.
Measles is a serious disease caused by a highly contagious virus, which spreads when people touMeasles is a serious disease caused by a highly contagious virus, which spreads when people touch or breathe in infectious droplets passed by coughing and sneezing. Measles begins with fever followed by cough, runny nose, and conjunctivitis (“pink eye”). Infections of the middle ears, pneumonia, croup, and diarrhea are common complications. Measles encephalitis (an infection of the brain) occurs in 1 per 1,000 cases of natural measles, frequently resulting in permanent brain damage in the survivors. Approximately 5% of children (500 out of 10,000) with measles will develop pneumonia. In addition, 1 to 3 of every 1,000 children who get measles in the United States dies from the disease.
Death is more common in infants, in malnourished children, and among immunocompromised persons, including those with leukemia and HIV infection.
Subacute sclerosing panencephalitis (SSPE) is a rare fatal illness caused by ongoing measles virus infection of the brain. Symptoms of brain damage usually begin 7 to 10 years after infection. Death occurs 1-3 years after the onset of symptoms. Risk factors for developing SSPE include developing measles infection at a young age. The incidence of SSPE is estimated to be between 7-11 cases/100,000 cases of measles. Measles vaccine virus was not associated with SSPE.
Prior to licensure of the first measles vaccine in 1963, virtually every person in the U.S. got the measles by age 20. Since the vaccine became available, there has been a 99% reduction in the incidence of measles. However, measles is still being “imported” from other countries.
Because of intense misinformation about MMR in the United Kingdom, MMR vaccine coverage has declined across Europe, resulting in outbreaks of measles and mumps in multiple countries, including the United States and Canada, and congenital rubella in the Netherlands and Canada. There were 140 cases of measles in the United States in 2008; more than three quarters of these cases were linked to imported measles from another country; most of the cases were unimmunized American children.
Neisseria meningitidis, or the meningococcus, is a bacterium that can cause a life-threatening infection of the bloodstream, meningitis (infection of the brain and spinal cord coverings), or both. Symptoms may include fever, stiff neck, sore throat, headache, muscle aches, joint pain and swelling, shock, and seizures. Complications—in 11-19% of survivors—may include deafness and other neurologic impairment, and impaired circulation leading to gangrene and amputation of limbs. Death occurs in 10% to 14% of people with meningococcal disease, and is highest in infants and adolescents.
The epidemiology of N. meningitidis is highly variable, with differences in serogroups and disease incidence between geographic regions causing unpredictable outbreaks and epidemics. Vaccine against serogroup C in the United Kingdom has proven highly efficacious and to serogroup B in New Zealand. Prior to recommending universal MCV4 immunization for 11-12 year old children in the United States, the incidence of meningococcal disease was at its nadir of 0.35/100,000 although it has varied from 0.5 to 1.5 cases per 100,000 population over the preceding decades.
There are approximately 2,600 cases of meningococcal meningitis in the U.S. each year, mostly in children less than five years old. Children younger than two years old have the highest incidence, with a second peak incidence between 15 to 24 years of age. Close contacts of a person with meningococcal disease have a higher rate of infection and are at greatest risk in the first week of contact. Depending on the type of exposure some of these persons may be given antibiotics to prevent infection. Studies report that first-year college students living in dormitories have a somewhat elevated risk for meningococcal disease when compared with other undergraduate students (See Related Issues).
Large outbreaks of the disease are rare in the United States, but not in some countries. It is recommended that travelers to certain areas, particularly sub-Saharan Africa during the dry season (December through June) and travelers to Mecca during Hajj receive the vaccine.
Mumps is a viral infection spread from person to person by secretions sneezed or coughed from the nose or throat.
Mumps usually begins with swelling and tenderness of one or more of the salivary glands. This lasts about a week. Complications can include inflamed testicles (20% to 50% of post-pubertal males infected), brain involvement including aseptic meningitis (15% of cases), and inflammation of the pancreas (2% to 5% of cases) and ovaries (5% of post-pubertal females). Permanent deafness occurs in 1 out of 2,000 cases.
The mumps virus has not been associated with problems during pregnancy, although there are some reports of an increase in fetal loss associated with mumps during the first trimester.
Before widespread vaccination, there were about 200,000 cases of mumps and 20 to 30 deaths reported each year in the United States. In 1998, there were just 600 cases of mumps and no fatalities reported from the disease.
Pertussis is a bacterial infection caused by Bordetella pertussis. The germ is spread when infected people cough or sneeze.
Children with pertussis have decreased ability to cough up respiratory secretions and develop thick, glue-like mucus in the windpipe. This causes severe coughing spells that make it difficult for them to eat, drink, or breathe. The child may suffer from coughing spells for two to three weeks or longer. Sometimes the child coughs several times before breathing in; when the child finally does breathe in there is often a loud gasp or “whooping” sound. The disease is most severe when it occurs early in life; it often requires hospitalization.
The majority of pertussis-related deaths are in young infants which may occur when other bacteria take the opportunity to invade the sick infant’s lungs. Primary pertussis pneumonia also may be life-threatening in infancy. In 1997, adolescents and adults accounted for 46% of reported cases of pertussis, and they are often the ones who spread this disease to infants and children.
Pertussis is one of the most contagious human diseases, so it is a great risk to those who are unvaccinated. Pertussis will develop in 90% of unvaccinated children living with someone with pertussis, and in 50% to 80% of unvaccinated children who attend school or daycare with someone with pertussis. Approximately 50 out of every 10,000 people who develop pertussis die from the disease. Between 1940-1945, before widespread vaccination, as many as 147,000 cases of pertussis were reported in the United States each year, with approximately 8,000 deaths caused by the disease. In 1976, there were 1,010 case of pertussis in the US, the lowest number of cases ever reported. Over the past few years the number of reported cases of pertussis has increased, reaching 25, 827 in 2004. Worldwide, there are an estimated 300,000 annual deaths due to pertussis.
In 2004, adolescents 11-18 years of age and adults 19-64 years of age accounted for 34% and 27% of the cases of pertussis in the US. The true numbers are probably much higher in these age ranges because pertussis is often not recognized in adults. These cases are very important because teenagers and adults with pertussis can transmit the infection to other people, including infants who are at greatest risk for complications and death. Recommendations for the use of newly licensed vaccines for adolescents and adults have recently been published.
Streptococcus pneumoniae are a group of bacteria also known as pneumococci. Pneumococci live in the nose and throats of people of all ages. Pneumococci can infect many different sites, some common—like the middle ear and the sinuses—and some less common but more serious, including the lungs (pneumonia), central nervous system (meningitis), and blood stream (bacteremia).
Serious pneumococcal infections are most common in infants, toddlers, smokers, and the elderly. In addition, people with certain health problems (e.g., immune deficiencies, sickle cell disease, lack of a functioning spleen) are at high risk for acquiring invasive pneumococcal disease. Children from African-American and Native American populations also have higher rates of invasive (serious) pneumococcal disease than white children.
A heptavalent pneumococcal conjugate vaccine (PCV7 vaccine), containing the 7 most common pneumococcal serotypes causing invasive infections in children in North America was licensed in the US and Europe and recommended for routine use in infants in 2000. The PCV7 vaccine has dramatically reduced the rates of invasive pneumococcal disease, otitis media and nasal carriage of the vaccine serotypes among all age groups, including the immunocompromised and older individuals. The vaccine has also reduced the racial disparities in pneumococcal disease. PCV7 has proven to be a cost effective vaccine because of the disease it prevents in young children. Vaccinating children against pneumococcus also has provided protection to their family members and the communities where they live, making it a cost saving vaccine when its effects on community immunity are considered. However, while the PCV7 vaccine has reduced pneumococcal disease caused by the seven most common types causing infection in children, there are other pneumococcal types which can also cause serious infections in children. Surveillance suggests an increase in disease in children aged < 5 years due to these nonvaccine serotypes, especially serotypes 3, 7F, and 19A, some of which are antibiotic resistant. Because children are the reservoir for the serotypes that cause invasive disease in older people, broadening the coverage of serotypes in the vaccine is desirable.
In 2010/2011 a 13-valent pneumococcal conjugate vaccine (PCV13) was licensed. PCV13, will protect against the same seven strains that were in PCV7 but also has the potential to further reduce the amount of invasive pneumococcal disease caused by 6 additional strains, including 3, 7F and 19A.
Since 2009/2010 an other 10-valent pneumococcal conjugate vaccine is available in Europe. This vaccine has an innovative design. It contains polysaccharides derived from 10 different strains of pneumococcal bacteria most of which are conjugated to protein D from non-typeable Haemophilus influenzae (NTHi). This paediatric pneumococcal vaccine protects against life-threatening diseases such as meningitis and bacteraemic pneumonia, as well as middle ear infections.
Polio is caused by intestinal viruses that spread from person to person in stool and saliva. Most people infected with polio (approximately 95%) show no symptoms. Minor symptoms can include sore throat, low-grade fever, nausea, and vomiting. Some infected persons (1 to 2%) will have stiffness in the neck, back, or legs without paralysis. Less than 1% of polio infections (about 1 of every 1,000 cases) cause paralysis. In some cases, the poliovirus will paralyze the muscles used to breathe, leaving the victim unable to breathe on his or her own. Many paralyzed persons recover completely. Those who do recover from paralytic polio may be affected 30 to 40 years later, with muscle pain and progressive weakness.
Before the polio vaccine, 13,000 to 20,000 people were paralyzed by polio, and about 1,000 people died from it each year in the United States. Most of those infected were elementary school children so it was often called ‘infantile paralysis.’
The incidence of paralytic polio peaked in the U.S. in 1952 with 21,000 reported cases and numerous deaths. Following licensure of the Salk (inactivated) polio vaccine in 1955, the incidence of the disease fell dramatically. The disease was further reduced by the advent of the Sabin (oral) polio vaccine in 1961. The last cases of paralytic polio from natural poliovirus in the U.S. were in 1979, and the most recent case from outside the U.S. occurred in 1993.
Today, polio has been eliminated from the U.S. and the entire Western Hemisphere, although it remains a threat in some countries. The World Health Organization set up an initiative to eradicate polio from the planet by the end of 2005.
Rabies is an acute and deadly disease caused by a viral infection of the central nervous system. The rabies virus is most often spread by a bite and saliva from an infected (rabid) animal (e.g., bats, raccoons, skunks, foxes, ferrets, cats, or dogs). In the United States, rabies is most often associated with bat exposures. However, there have been rare cases in which laboratory workers and explorers in caves inhabited by millions of bats were infected by rabies virus in the air.
Virtually 100% of those infected with rabies who do not receive the vaccine will die. Rabies illness includes rapidly progressing central nervous system symptoms such as anxiety, difficulty swallowing, and seizures.
Although less than ten human rabies fatalities occur in the United States annually, as many as 40,000 Americans receive the vaccine each year after contact with animals suspected of being rabid. An additional 18,000 people get the vaccine before exposure as a preventative measure.
Worldwide, at least 4 million people are vaccinated each year for rabies. The number of deaths that rabies causes each year is estimated to be at least 40,000, and as high as 70,000 if higher case estimates are used for densely populated countries in Africa and Asia where rabies is epidemic. India, with a very large population of stray, ownerless dogs, has about half of all cases of rabies worldwide. Between 30-60% of human rabies cases occur in children under 15 years of age.
Prompt wound care and the administration of rabies immune globulin (RIG) plus vaccine are highly effective in preventing human rabies following exposure.
Rotaviruses are intestinal viruses that infect virtually all children by three years of age. It is the most common cause of diarrhea in children, including hospital-acquired diarrhea; childcare center outbreaks are common. The illness often also includes fever and vomiting, lasts a week or longer, and can cause persistent infection in immunocompromised people. Most rotavirus infections are mild, but about 1 in 50 cases develop severe dehydration. Each year in the United States, rotavirus infections resulted in 22.5 hospitalizations and 301 emergency room visits per 10,000 children less than 3 years of age. That is, 1 in 150 children were hospitalized because of rotavirus infection and another 1 in 11 visited an emergency room or visited an outpatient clinic for rotavirus infection. In developing countries, rotavirus leads to an estimated 480,000 to 640,000 deaths each year.
Rubella is caused by a virus that is transmitted from person to person in mucus droplets coughed or sneezed into the environment. Rubella usually is a mild illness. Symptoms include low-grade fever and swollen lymph nodes in the back of the neck followed by a generalized rash. Complications may include joint pain, a temporary decrease in platelets, and encephalitis (inflammation of the brain). Temporary arthritis may also occur, particularly in adolescents and adult women.
Rubella in expectant women often leads to congenital rubella syndrome (CRS) in their fetuses. This is a devastating disease characterized by deafness, mental retardation, cataracts and other eye defects, heart defects, and diseases of the liver and spleen that may result in a low platelet count with bleeding under the skin. The incidence and severity of congenital defects are greater if infection occurs during the first month of gestation. Up to 85% of expectant mothers infected in the first trimester will have a miscarriage or a baby with CRS.
The World Health Organization estimated that, in 1999, 110,000 infants were born with CRS worldwide. Although most CRS occurs in developing countries, it also continues to occur in the U.S., mostly among unimmunized Hispanics.
Before a vaccine was available, there was a rubella outbreak in the U.S. (1963 to 1964), during which 12 million people developed the disease. Because many of those infected were expectant mothers, 11,000 fetuses died and 20,000 babies were born with permanent disabilities as a result of exposure to the virus. The number of cases of rubella fell very sharply once the rubella vaccine was licensed in 1969; today there are fewer than 1,000 cases of rubella reported each year in the U.S. on average and less than 10 cases of congenital rubella syndrome.
Because of intense misinformation about MMR in the United Kingdom, MMR vaccine coverage has declined across Europe, resulting in outbreaks of measles and mumps in multiple countries, including the United States and Canada, and congenital rubella in the Netherlands and Canada. There were 42 cases of rubella among pregnant women with two fetal deaths and 12 affected infants. Ironically, one of the few known causes of autism was the congenital rubella syndrome, autism having occurred in 20% of rubella-affected babies prior to the licensure of rubella vaccine. MMR vaccine, therefore, protects against autism by preventing congenital rubella syndrome.
Zoster (shingles) is an infection caused by the varicella-zoster virus (VZV), the cause of chickenpox. The VZV virus—which remains in the nerve cells for life after chickenpox or after the chickenpox vaccine—may reappear as shingles in later life, particularly in the elderly and those who are immunocompromised. This is because of declining immunity to the VZV virus over time. Thus, anyone who has had chicken pox or the chickenpox live virus vaccine is at risk for developing shingles. While shingles can occur at any age, the risk increases as people get older. When shingles develop, a rash or blisters appear on the skin, generally on one side of the body. The skin blisters in shingles contain the VZV virus so chickenpox-susceptible children can develop chickenpox when exposed to shingles.
Because the infection in shingles starts in the nerves, shingles can also be painful. Pain can last for months after the rash has healed and can be very severe—this is called post herpetic neuralgia or PHN. Shingles occurs most commonly in older individuals and PHN is a more common complication of shingles in older individuals.
Most people in the U.S.—indeed in the world—have not considered smallpox a health threat for several decades. Smallpox hasn’t occurred in the U.S. since 1949, and routine vaccination against it ended here in 1972. When the World Health Organization (WHO) certified that smallpox had been eradicated from the planet in 1980, this was the first time in history that medical scientists and public health workers had completely purged the world of a devastating infectious disease.
Though the disease was eradicated over 20 years ago, several samples of the live virus were preserved, mainly for research purposes. Today the only verified repositories of the virus are held in secure laboratories at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and the State Center for Research on Virology and Biotechnology in Koltsovo, Russia. However, it is believed that clandestine stocks of smallpox exist in 10 or more other countries.
Due to the events of September 11, 2001, and the subsequent spread of anthrax in October, public health officials regard the use of biological weapons by terrorists as a real possibility. The Congressional testimony of former Soviet scientist, Kenneth Alibek, supports this view. Alibek said that as recently as the early 1990s, dozens of tons of smallpox were being stockpiled in the former Soviet Union annually for use as weapons. He also reported that some of the more than 60,000 people involved in biological weapons research for the former Soviet government may be employed by governments wishing to develop biological weapons. Read Alibek’s testimony before Congress at www.house.gov/jec/hearings/intell/alibek.htm. Most recently, a CIA intelligence review concluded that Iraq, France, North Korea, and Russia have covert stocks of smallpox virus, although the French government has denied the allegation. Of all the disease-causing agents that might be used as weapons, smallpox has the potential to cause the greatest harm, since, prior to its eradication, it was considered the most devastating of all infectious diseases.
Smallpox is caused by the variola virus, which can be spread from person to person via respiratory droplets produced in the nose, mouth, and throat of someone who is infected and has begun to show signs of illness. After a person has been exposed to the virus, there is an incubation period of between 7 and 17 days prior to the onset of symptoms, which include high fever, severe headache and backache, and often vomiting and tremors. Two to five days later, the characteristic smallpox rash develops. It begins as flat, round lesions, primarily on the face and forearms, and evolves into deep, pus-filled blisters that may cover the entire body, including the palms and soles of the feet. Some patients have a fever throughout the course of the rash (two to four weeks), and often the blisters cause significant pain. In the last stage of the rash scabs form and fall off, leaving pitted scars. Some smallpox survivors are blind as a result of deep scarring in the eye area. Smallpox during pregnancy often results in miscarriage or stillbirth.
In the first two to three days of the rash, smallpox can be confused with chickenpox (varicella). However, chickenpox lesions generally develop in crops over a period of several days and are much more superficial than smallpox lesions. Chickenpox lesions in one area may be in different stages of development (macule, papule, and pustule). In contrast, smallpox lesions in any area are all at the same stage in development and, in addition, smallpox lesions may have a small dimple in their center. Chickenpox lesions generally occur on the torso, while the smallpox rash is most prominent on the face and extremities. Also, chickenpox lesions occur much less frequently on the palms or soles of the feet.
A timeline of disease development is available at the CDC smallpox website, www.cdc.gov/smallpox.
The smallpox patient is most contagious during the first week of the rash, when the virus is most abundant in the saliva. But the disease remains transmissible to others until all the scabs have fallen off.
Historically, the two most prevalent forms of smallpox were variola major, which caused severe illness and killed about 30% of unvaccinated persons, and variola minor, which caused a much milder form of illness and had about a 1% death rate. Two less common forms of the disease were even more deadly. Malignant smallpox, noted by its abrupt onset and by its flat, velvety lesions that never became pustular, caused death in more than 96% of people affected. Hemorrhagic-type smallpox caused bleeding into the skin and other body parts and was almost always fatal within less than a week of the appearance of a rash. Pregnant women were highly susceptible to hemorrhagic-type smallpox.
Tetanus (Lockjaw) is caused by toxin-producing spores of a bacterium Clostridium tetani that inhabit the soil and the bowels of animals and humans. Unlike other vaccine-preventable diseases, it is not spread from person to person. Tetanus may occur following delivery in the newborn babies of unimmunized women. Tetanus infection is most often the result of wound contamination in an unimmunized person or someone who has not had vaccine boosters in many years. It may also occur following puncture wounds, animal bites, burns, abrasions and surgery.
The tetanus toxin causes severe muscle contractions, or spasms. Fever, sweating, elevated blood pressure, and rapid heart rate may also occur. Spasms of the vocal cords or the muscles of respiration can interfere with breathing, and pneumonia is common. Contraction of muscles can be so severe that the spine or other bones are fractured.
Between 40-60 cases of tetanus are reported in the United States each year, and 30% of those infected with tetanus in the US die. Death is more likely in newborn infants of unimmunized mothers and patients over 50.
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. It is generally spread in mucus droplets coughed out by infected people.
Most people with tuberculosis show no symptoms at the time of infection. People who develop symptoms usually do so within one to six months after the start of the infection. Symptoms include fever, night sweats, chills, and cough. Pneumonia, lung collapse, and enlarged lymph nodes may also occur.
The most common form of tuberculosis affects the lungs. Two forms of tuberculosis that become life-threatening are:
- Miliary TB, which means the bacteria have spread throughout the lungs and into the bloodstream
- TB meningitis (infection of the coverings of the spinal cord and/or brain by TB bacteria)
More than 25,000 new cases of TB are reported annually in the United States. People who are immunocompromised (have weakened immunity), especially those who are HIV-positive, are at increased risk of developing TB if they are exposed to the disease. Malnourished people as well as those with diabetes or kidney failure are also more likely to develop the disease if exposed.
TB kills more people in the world than does any other infection. Someone in the world is newly infected with TB bacilli every second. Overall, one-third of the world’s population is currently infected with the TB bacillus.
Typhoid fever is a serious disease caused by the bacterium called Salmonella enterica serotype Typhi (S. Typhi).
The infection is spread from person-to-person by the fecal-oral route. That means that people get typhoid from food or water contaminated with the feces of infected people.
Typhoid symptoms include high fever, weakness, stomach pains, headache, loss of appetite, and sometimes a rash. Infection can spread to many other places in the body (such as bones) and can cause rupture of the intestine. It kills up to 30% of people who get it, if they are not treated.
Some people who become infected with S. Typhi become chronic carriers—they have no symptoms but have S. Typhi in their feces. Chronic carriers can spread S. Typhi to other people especially when handling food.
Antibiotic therapy reduces deaths and complications caused by typhoid fever. However, in recent years S. Typhi has acquired resistance to many of the antibiotics most widely available for its treatment. Typhoid vaccine can reduce the risk of illness in those who are exposed to S. Typhi.
According to the World Health Organization, 16 million people get typhoid every year around the world and about 600,000 die from the disease.
Typhoid is not common in the United States. Although 356 cases of typhoid fever were reported in the US in 2003, most of these infections are acquired during travel to other parts of the world or by contact with someone who is a carrier—either someone who has recently traveled or is a chronic carrier of S.Typhi.
Varicella (chickenpox) is an infection caused by the varicella-zoster virus (VZV). The infection usually starts as a rash on the face that spreads to the rest of the body. The rash begins as red bumps that eventually become blisters. A child will often get 300 to 500 blisters during the infection, which crust over and fall off in one to two weeks. The virus can be spread in the fluid from the blisters or droplets from an infected person’s nose or throat.
Varicella is generally a mild disease, but it is highly contagious and can be severe and even fatal in otherwise healthy children (less than 1 out of every 10,000 cases). Chickenpox can cause pneumonia (23 out of every 10,000 cases), and is an important risk factor for developing severe invasive “strep” (group A streptococcal disease), commonly referred to as “flesh-eating disease.” Treatment of this deep infection requires antibiotics and surgery to remove the infected tissue. Complications of varicella include bacterial infections (up to 5% of cases), decreased platelets, arthritis, hepatitis, and brain inflammation (1 in 10,000 cases), which may cause a failure of muscular coordination. Complications are more common among adolescents and adults, and in immunocompromised persons of all ages, than in children.
The virus which causes chickenpox remains in the body for life and may reappear as shingles, particularly in the elderly. A woman who contracts chickenpox in early pregnancy can pass the virus to her fetus, causing abnormalities in 2% of cases. The fetus can develop scarring of the skin and affected limb(s), limb deformities (hypoplesia), eye damage, low birth weight, brain atrophy, and mental retardation. The virus sometimes leads to fetal demise or spontaneous abortion, while some infected fetuses die in infancy. A pregnant woman who has never had chickenpox, but has been exposed, should contact her physician immediately. Prior to the introduction of the varicella vaccine, there were 3 to 4 million cases of varicella in the United States each year. About 10,000 people were hospitalized with complications, and approximately 100 patients died. While only 5% of reported cases of varicella are in adults, adults account for 35% of the deaths from the disease.
Although national figures demonstrating the decline in varicella are not yet available, smaller-scale studies show that the vaccine is effective in reducing the number and severity of chickenpox cases. A number of studies have demonstrated that varicella-containing vaccines are effective in preventing disease in large populations of students. However, when chickenpox exposure occurs, breakthrough chickenpox (that is chickenpox lesions in an immunized person) can occur. Most children who are immunized but later develop chickenpox have mild disease, although some may have more typical illness with fever and many lesions. Breakthrough varicella can be contagious. As a consequence, in June 2006, the Centers for Disease Control and Prevention recommended a second dose of varicella-containing vaccine for all children.
In 2005 a combination measles, mumps, rubella, varicella vaccine was licensed.
Yellow fever is caused by a virus that is carried by a biting mosquito. Only humans and monkeys can be naturally infected with yellow fever virus. A mosquito that is capable of transmitting yellow fever virus is present in southern parts of the United States.
Epidemic yellow fever used to occur in the United States but now the disease occurs only in sub-Saharan Africa and tropical South America, where it is endemic and intermittently epidemic. There are 200,000 estimated cases of yellow fever (with 30,000 deaths) per year. However, due to underreporting, only a small percentage of these cases are identified. Small numbers of imported cases also occur in countries free of yellow fever.
Infection causes a wide spectrum of disease. Most cases of yellow fever are mild and similar to influenza, consisting of fever, headache, nausea, muscle pain and prominent backache. After three to four days most patients improve and their symptoms disappear. However, in about 15% of patients, fever reappears after 24 hours with severe illness which includes hepatitis and hemorrhagic fever. Bleeding can occur from the mouth, nose, eyes and/or stomach. Once this happens, blood appears in the vomit and feces. Kidney function also deteriorates. Half of those who develop the severe illness die within 10-14 days. The remainder recovers without significant organ damage.
The “yellow” in the name is explained by the jaundice that occurs with hepatitis.
Source: Source: Nnii (National Network for Immunization Information) – October 15th, 2012 (last updated)