Childhood infectious diseases

• ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, immune system, lungs, muscles, musculoskeletal system, nose, respiratory system

DEFINITION: A group of diseases including diphtheria, tetanus, measles, polio, rubella (German measles), mumps, varicella (chickenpox), hepatitis, and pertussis (whooping cough)

Causes and Symptoms

Acute communicable diseases occur primarily in childhood because most adults have become immune to such diseases, either by having acquired them as children or by having been inoculated against them. For example, prior to the use of vaccines for measles—a highly contagious disease found in most of the world—the peak incidence of the disease was in five- to ten-year-olds. Most adults were immune. Before a vaccine was developed and used against measles, epidemics occurred at two- to four-year intervals in large cities. Most modern cases are found in non-immunized preschool children or in teenagers or young adults who have received only one dose of the vaccine. Separate vaccines for the measles, mumps, and rubella (MMR) were developed in the 1960s, and the combined MMR vaccine was released in 1971.

Measles, a highly contagious virus, is a leading cause of fatalities among children worldwide. According to the World Health Organization, there were 107,500 measles deaths worldwide in 2023, mostly children under five who were unvaccinated or undervaccinated. Between 2000 and 2023, measles vaccination worldwide prevented an estimated 60 million deaths. A person infected with red measles (also known as rubeola) becomes contagious about ten days after exposure to the disease virus, at which time the prodromal stage begins. Typically, the infected person experiences three days of slight to moderate fever, a runny nose, an increasing cough, and conjunctivitis. During the prodromal stage, Koplik’s spots appear inside the cheeks opposite the lower molars. These lesions—grayish white dots about the size of sand particles with a slightly reddish halo surrounding them that are occasionally hemorrhagic—are important in the diagnosis of measles.

After the prodrome, a rash appears, usually accompanied by an abrupt increase in temperature (sometimes as high as 104 or 105 degrees Fahrenheit). It begins in the form of small, faintly red spots and progresses to large, dusky red confluent areas, often slightly hemorrhagic. The rash frequently begins behind the ears but spreads rapidly over the entire face, neck, upper arms, and upper part of the chest within the first twenty-four hours. During the next twenty-four hours, it spreads over the back, abdomen, entire arms, and thighs. When it finally reaches the feet after the second or third day of the rash, it is already fading from the face. At this point, the fever usually disappears as well.

The chief complications of measles are ear infections, pneumonia, and encephalitis (a severe infection of the brain). In some cases of measles, patients may develop acute post-infectious measles encephalitis (APME), but the incidence of the infection of the brain runs to only one or two per every thousand cases. Measles can also exacerbate tuberculosis.

The incubation period for rubella (German measles) lasts between fourteen and twenty-one days, and the disease occurs primarily in children between the ages of two and ten. Like the initial rash of measles, the initial rash of rubella usually starts behind the ears, but children with rubella normally have no symptoms save for the rash and a low-grade fever for one day. Adolescents may have a three-day prodromal period of malaise, runny nose, and mild conjunctivitis; adolescent girls may have arthritis in several joints that lasts for weeks. The red spots begin behind the ears and then spread to the face, neck, trunk, and extremities. This rash may coalesce and last up to five days. Temperature may be normal or slightly elevated. Complications from rubella are relatively uncommon, but if pregnant women are not immune to the disease and are exposed to the rubella virus during early pregnancy, severe congenital anomalies or miscarriage may result. Because similar symptoms and rashes develop in many viral diseases, rubella is difficult to diagnose clinically. Except in known epidemics, laboratory confirmation is often necessary.

The patient with mumps is likely to have fever, malaise, headache, and anorexia—all usually mild—but “neck swelling,” a painful enlargement of the parotid gland near the ear, is the sign that often brings the child to a doctor. Maximum swelling peaks after one to three days and begins in one or both parotid glands, but it may involve other salivary glands. The swelling pushes the earlobe upward and outward and obscures the angle of the mandible. Drinking sour liquids such as lemon juice may increase the pain. The opening of the duct inside the cheek from the affected parotid gland may appear red and swollen.

The painful swelling usually dissipates by seven days. Abdominal pain may be caused by pancreatitis, a common complication, but one that is usually mild. The most feared complication, sterility, is not common. Orchitis rarely occurs in prepubertal boys and occurs in 20 to 30 percent of older males. In 35 percent of patients with orchitis, both testes are involved, and a similar percentage of affected testes will atrophy. Surprisingly, impairment of fertility in males is only about 13 percent; absolute infertility is rare. Ovary involvement in women, with pelvic pain and tenderness, occurs in only about 7 percent of postpubertal women and with no evidence of impaired fertility. Mumps during early pregnancy may cause miscarriage, but this is a rare complication for immunized patients.

Haemophilus influenzae type B (Hib) is a common cause of serious bacterial infection in young children. Prior to the introduction of the Hib vaccine, it was the leading cause of bacterial meningitis in children under the age of five. It can cause many other serious, life-threatening bacterial infections in young children. Bacterial meningitis, especially from H. influenzae and pneumococcus, is the major cause of acquired hearing impairment in childhood.

Poliomyelitis (polio), an acute viral infection, can have a wide range of manifestations. Symptoms of polio include slight fever, malaise, headache, sore throat, and vomiting, but do not involve the central nervous system in mild cases. Major illness occurs primarily in older children and adults. It may begin with fever, severe headache, stiff neck and back, deep muscle pain, and abnormal sensations, such as burning, prickling, tickling, or tingling. These symptoms of aseptic meningitis may go no further or may progress to the loss of tendon reflexes and asymmetric weakness or paralysis of muscle groups. One in two hundred polio infections leads to irreversible paralysis; of those individuals who become paralyzed by polio, 5 to 10 percent die when their breathing muscles become affected. Efforts to eradicate the disease have dramatically reduced the number of cases worldwide. Following the introduction of the polio vaccine, the disease was eradicated in most countries, and the number of cases declined by more than 99 percent between 1988 and 2023; however, polio remained endemic in Afghanistan and Pakistan, where a resurgence began in the early 2020s. Additionally, numerous countries experienced a significant increase in circulating vaccine-derived poliovirus (cVDPV) in the mid-2020s, reaching 280 total cases in several nations in Africa. Following this increase, the Global Polio Eradication Initiative (GPEI) expressed concerns about the virus's potential to spread rapidly in areas of low immunization.

Tetanus is a bacterial disease that, once established in a patient's wound without significant immunity, will produce a substance that acts at the neuromuscular junction, the spinal cord, and the brain. Clinically, the patient experiences “lockjaw,” a tetanic spasm causing the spine and extremities to bend with convexity forward; spasms of the facial muscles cause the famous “sardonic smile.” Minimal stimulation of any muscle group may cause painful spasms. Tetanus kills about 10 to 20 percent of people who become infected.

Diphtheria is another bacterial disease that produces a virulent substance, but this one attacks the heart muscle and nervous tissue. There is a severe mucopurulent discharge from the nose and an exudative pharyngitis (a sore throat accompanied by phlegm) with the formation of a pseudomembrane. Swelling just below the back of the throat may lead to stridor (noisy, high-pitched breathing) and to the dark bluish or purplish coloration of the skin and mucous membranes because of decreased oxygenation of the blood. The result may be heart failure and damaged nerves; respiratory insufficiency may be caused by diaphragmatic paralysis.

Clinically, pertussis (whooping cough) can be divided into three stages, each lasting about two weeks. Initial symptoms resembling the common cold are followed by the characteristic paroxysmal cough and then convalescence. In the middle stage, multiple, rapid coughs, which may last more than a minute, will be followed by a sudden inspiration of air and a characteristic “whoop.” In the final stage, vomiting commonly follows coughing attacks. Almost any stimulus precipitates an attack. Seizures may occur as a result of hypoxia (inadequate oxygen supply) or brain damage. Pneumonia can develop, and even death may occur when the illness is severe. Approximately 2 percent of adolescents and 5 percent of adults with pertussis must be hospitalized or develop complications. Tetanus, diphtheria, and pertussis can all be prevented with the Tdap vaccine. After the Tdap vaccine was introduced, reported cases of tetanus and diphtheria declined by about 99 percent, and cases of pertussis fell by about 80 percent in the United States. However, in the 2020s, a global resurgence of pertussis began, even in vaccinated populations.

Varicella (chickenpox) produces a generalized itchy, blister-like rash with low-grade fever and few other symptoms. Minor complications, such as ear infections, occasionally occur, as does pneumonia, but serious complications, such as infection in the brain, are rare. It is a very inconvenient disease, however, requiring the patient to be quarantined for about nine days or until the skin lesions have dried up completely. Varicella, a herpes family virus, may lie dormant in nerve linings for years and suddenly emerge in the linear-grouped skin lesions identified as herpes zoster. These painful skin lesions follow the distribution of the affected nerve. Herpes zoster is commonly known as shingles; the shingles vaccine (Shingrix) became standard for older adults by the 2020s.

Hepatitis B is more common in children than adults in endemic regions, but in Europe and North America, it is more common in adults, primarily because of lifestyle-related transmission risks. High carrier rates appear in Eastern Europe, East Asia, the Pacific Islands, sub-Saharan Africa, and the Amazon Basin, where perinatal transmission is the most common means of perpetuating the disease. Having this disease in childhood can cause problems later in life. In the United States, the CDC reported an annual hepatitis B mortality rate of 0.44 deaths per 100,000 population in 2023. Carrier rates of between 5 and 10 percent result from disease acquired after the age of five, but between 80 and 90 percent will be carriers if they are infected at birth. The serious problems of hepatitis B, such as cirrhosis of the liver, occur most often in chronic carriers. For example, approximately 25 percent of carriers ultimately develop liver cancer or cirrhosis. The virus is fifty to one hundred times more infectious than human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). Health care workers are at high risk of contracting hepatitis B, but virtually everyone is at risk of contracting this disease because it is so contagious.

Hepatitis A is a virus that causes jaundice, fatigue, abdominal pain, nausea, diarrhea, and fever. Approximately 15 percent of those who have the disease will have relapsing symptoms for six to nine months. Hepatitis A is usually spread through fecal contamination. With the introduction of the hepatitis A vaccine in the 1900s, the incidence of hepatitis A in the United States declined from approximately 25,000 to 3,500 cases per year, though outbreaks occurred in the 2010s.

Treatment and Therapy

The Centers for Disease Control and Prevention (CDC) and the US Department of Health and Human Services have an established vaccine schedule that recommends vaccinations against hepatitis B, rotavirus, diphtheria, tetanus, pertussis, Haemophilus influenzae type b, pneumococcal disease, poliovirus, influenza, measles, mumps, rubella, varicella, meningococcal disease, hepatitis A, and human papillomavirus (HPV). The CDC recommends immunizing all infants against hepatitis B soon after birth and again at age one to two months, with a final dose at six to eighteen months. The Committee on Infectious Diseases of the American Academy of Pediatrics recommends extending hepatitis B immunization to all adolescents, if possible. Field trials showed the hepatitis B vaccine to be more than 90 percent effective with all three doses. The vaccine is protective against chronic hepatitis B infection for at least twenty years among individuals who receive their first vaccine before they reach six months old.

The incidence of infection with hepatitis B increases rapidly in adolescence, but teenagers are less likely to comply with immunization than are infants. Asking adolescents to participate in a three-dose immunization program over a six-month period is likely to result in high dropout rates. Therefore, the American Academy of Pediatrics has recommended combining vaccination at birth with vaccination of teenagers. Hepatitis A vaccine is recommended by the CDC for all children between twelve and twenty-three months of age. Two doses of the vaccine should be given, separated by six to eighteen months.

Primary vaccination with DTaP (diphtheria, tetanus, and acellular pertussis) vaccine is recommended at two months, four months, and six months of age, followed by boosters at fifteen to eighteen months and upon entry into school (at four to six years of age).

Primary vaccination of the Haemophilus influenzae type B vaccine should occur at two months, four months, and six months, with a booster shot at twelve to fifteen months of age. Three vaccines are licensed for use in infants. Depending on which vaccine is used, shots are given at ages two, four, and six months, with a booster between twelve and fifteen months. These vaccines are safe and 90 to 95 percent effective in preventing serious illness.

At two and four months of age, infants should receive inactivated poliovirus vaccinations, with boosters between six and eighteen months and upon entry into school (four to six years of age).

MMR (measles, mumps, rubella) vaccination should take place at twelve and fifteen months and at four to six years of age. If the infant lives in a high-risk area, the first dose should occur at twelve months of age. Those who are pregnant or plan to become pregnant in the next four weeks should not receive the MMR vaccination. Children may receive the vaccine even if their mother is pregnant, since the viruses are not shed by immunized individuals. Children who have not received the second dose should be vaccinated at eleven to twelve years.

In the 1990s, researchers announced that they had developed a vaccine to prevent chickenpox. According to the CDC, the first dose of the varicella vaccine should be given to children between twelve and fifteen months of age who have not had chickenpox. The second dose is given between ages four and six, but may be given as soon as three months after the first dose. Individuals aged thirteen and older who have never had chickenpox or the vaccine should get two doses given at least twenty-eight days apart. The chickenpox vaccine is contraindicated for those who have had life-threatening allergic reactions to a prior dose of the vaccine, gelatin, or neomycin; children taking aspirin or other salicylates should not receive the vaccine. Those who are ill or pregnant at the scheduled vaccination time should postpone vaccination. Those who have immune system diseases, are taking drugs that affect the immune system, have cancer, are receiving cancer treatments, or have had a recent blood transfusion or other blood products should check with their physician before receiving the vaccine.

The CDC states that a combination vaccine called MMRV containing both chickenpox and MMR vaccines can be given instead of the two individual vaccines to children twelve and under. The combination vaccine is associated with a rash and higher rates of fever compared to the two vaccines administered separately; febrile seizures, although rare, are also more frequently reported with the combination vaccine.

Influenza vaccine, containing two strains of type A and one strain of type B, is recommended to be administered to all children older than six months to prevent infection with seasonal influenza viruses. Annual vaccination is necessary as influenza viruses continually mutate, resulting in new strains not present in previous vaccines. Sometimes, special strains of influenza, such as H1N1 (swine) influenza, may necessitate adding a separate influenza vaccine. Vaccination is particularly important for children with chronic heart and lung disease, diabetes, HIV, sickle cell disease, and other chronic conditions that place them at greater risk for severe influenza.

Pneumococcal vaccine is now routinely given to children aged two to twenty-three months and to certain children aged twenty-four to fifty-nine months who are at risk of overwhelming pneumococcal infections. For example, children without spleens and children with sickle cell disease should be considered for vaccination against pneumococcal disease.

The Centers for Disease Control and Prevention and the American Academy of Pediatrics recommend HPV vaccinations for all young people beginning between the ages of nine and twelve. For those who receive their vaccination before the age of fifteen, two doses should be given six to twelve months apart. However, for some patients, such as those who are immunocompromised or those who begin vaccination after the age of fifteen, experts recommend three doses.

In 2023, the US Food and Drug Administration approved a respiratory syncytial virus (RSV) preventive antibody treatment, nirsevimab (Beyfortus), for infants.

Meningococcal vaccine, which protects against bacteremia and meningitis caused by some strains of meningococci, should be given to children with certain immune deficiency states, including the absence of a functioning spleen. The vaccine may also be given if there is an outbreak of meningococcal disease caused by a strain included in the vaccine, or if the child is traveling to a part of the world where the disease is common. Routine meningococcal vaccination is administered at eleven to twelve years with a booster dose at sixteen years.

Some parents refuse to have their children vaccinated because of concerns about vaccine safety. Media focus on the safety of pertussis vaccines, as well as lawsuits, has frightened many physicians as well, resulting in them being overly cautious in interpreting vaccine contraindications. Yet primary care physicians have also been sued for failing to give timely immunizations, which may result in complications from preventable diseases. Vaccine safety information is available, including reports from the American Academy of Pediatrics Task Force on Pertussis and Pertussis Immunization. Some parents have feared that there is a link between vaccinations and neurological disorders such as autism, but studies have found no connection.

The means exist to prevent many serious illnesses from infectious diseases in childhood, but both parents and health care professionals must make the effort to vaccinate all children at the appropriate times in their lives. Other common infectious diseases of childhood that do not have an associated vaccination include upper respiratory viral and bacterial infections, such as colds, bronchiolitis, or croup; ear infections, sinusitis, impetigo, and conjunctivitis.

Perspective and Prospects

Some vaccines are more effective than others; their effectiveness may hinge on several factors. In 1989, for example, 40 percent of people who developed measles had been vaccinated correctly under the old guidelines of one dose. Recommendations were therefore revised to include a booster dose. In the case of the hepatitis B vaccine, initial recommendations for administration of the vaccine established no injection site (only intramuscular), but studies revealed that there were fewer vaccine failures in recipients who were vaccinated in the deltoid region of the arm as opposed to the buttocks. The recommendation for the injection site was therefore revised.

In the United States, vaccine coverage increased in the late 1990s after having been woefully inadequate during the 1980s. One state’s department of health, in a 1987 study, discovered that only 64 percent of children who were two years old were adequately vaccinated with DTaP, oral polio, and MMR vaccines. The COVID-19 pandemic in 2020 led to additional setbacks in vaccinations due to lockdowns and sickness. By 2000, rates were closer to 80 percent, and in 2014, the rates had risen to more than 90 percent. Multiple and interacting factors have inhibited full vaccine coverage for all American children, including physicians’ attitudes and practice behaviors. For parents, the cost of vaccination, lack of health insurance, and other barriers to health care frustrate their efforts to get their children immunized. Some parents, for ideological or other reasons, may even be disinterested in or opposed to vaccination. According to the CDC, during the 2020-2021 school year, national coverage among kindergarten students declined from about 95 percent to about 94 percent. Coverage dropped again during the 2021-2022 school year, with only about 93 percent of all kindergarten students receiving national coverage. According to the World Health Organization (WHO), as of 2022-2023, the number of children receiving all recommended vaccinations returned to pre-pandemic levels, and the proportion of children receiving their first dose of the measles vaccine dropped from 86 percent in 2019 to 83 percent in 2023.

Meanwhile, the CDC reported that the number of children with at least one vaccine exception rose from 2.6 percent in 2021-2022 to 3 percent in 2022-2023, and to 3.6 percent in the 2024-2025 school year.

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