Introduction: Viral Infections: Merck Manual Home Edition


	Section		Children's Health Issues

	Subject		Viral Infections

Introduction

Viral infections are common among people of all ages but often seem to be concentrated in infants and children. Most childhood viral infections are not serious and include such diverse illnesses as colds with a sore throat, vomiting and diarrhea, and fever with a rash. Some viral illnesses that cause more serious disease, such as measles, are less common now due to widespread immunization. Several types of viral infections that children can acquire are discussed in the chapter on adult viral infections (see Viral Infections: Introduction).

Most children with viral infections get better without treatment, and many viral infections are so distinctive that a doctor can diagnose them based on their symptoms. A doctor usually does not need to have a laboratory identify the specific virus involved.

Many viral infections result in fever and body aches or discomfort. Doctors treat these symptoms with acetaminophen or ibuprofen. Aspirin is not given to children or adolescents with these symptoms, because it increases the risk of Reye's syndrome in those who have certain viral infections. Generally, parents can discern whether their child is ill with a potentially serious infection and needs immediate medical care. This is particularly true for children beyond infancy.

What Is Reye's Syndrome?

Reye's syndrome is a very rare but life-threatening disorder that causes inflammation and swelling of the brain and degeneration of the liver.

The cause of Reye's syndrome is unknown, although it typically occurs after infection by certain viruses, such as influenza or varicella (chickenpox), particularly in children who take aspirin. Because of this increased risk of Reye's syndrome, aspirin is not recommended for children, except for the treatment of a few specific diseases. Now that aspirin use has declined—in large part because of the possibility of triggering Reye's syndrome—fewer than 20 children a year develop this disorder. The condition occurs mainly in children younger than 18. In the United States, most cases occur in late fall and winter.

Reye's syndrome begins with the symptoms of a viral infection, such as an upper respiratory tract infection, influenza, or chickenpox. After 5 to 7 days, the child suddenly develops very severe nausea and vomiting. Within a day, the child becomes confused, disoriented, and agitated. These changes in the child's mental condition are sometimes followed by seizures, coma, and death. Degeneration of the liver may lead to blood clotting problems and bleeding. The severity of illness varies greatly. Doctors obtain blood tests and often perform a liver biopsy (the removal of tissue samples for examination) to confirm the diagnosis and to rule out other diseases.

The child's prognosis depends on the amount of swelling in the brain. The overall chances that the child will die are about 20%, but range from less than 2% among children with mild disease to more than 80% among those in a deep coma.

Children who survive the acute phase of the illness usually recover fully. Those with more severe symptoms may later show some evidence of brain damage, such as mental retardation or a seizure disorder. Abnormal muscle movement or damage to specific nerves may also occur. Reye's syndrome rarely affects a child twice.

There is no specific treatment for Reye's syndrome. Children are placed in intensive care. Vitamin K or fresh frozen plasma is given to help prevent bleeding. Children in a deep coma may require placement of a tube into the windpipe to assist their breathing (endotracheal intubation). To alleviate the swelling and pressure on the brain, doctors restrict fluids, elevate the head of the bed, and give drugs that force the body to get rid of excess water (such as mannitol).

Some Viral Infections At a Glance
Infection	Period of Incubation	Period of Contagiousness	Site of Rash	Nature of Rash
Measles (rubeola)	7 to 14 days	From 2 to 4 days before the rash appears until 2 to 5 days after	Starts around the ears and on the face and neck; in more severe cases, spreads over the trunk, arms, and legs	Irregular, flat, red areas that soon become raised; begins 3 to 5 days after the onset of symptoms; lasts 3 to 5 days
Rubella (German measles)	14 to 21 days	From shortly before the onset of symptoms until the rash disappears; infected newborns are usually contagious for many months	Starts on the face and neck; spreads to the trunk, arms, and legs	Fine, pinkish, flat rash; begins 1 or 2 days after the onset of symptoms; lasts 3 to 5 days
Roseola infantum (exanthem subitum, pseudorubella)	About 5 to 15 days	Unknown	The chest and abdomen, with moderate involvement of the face, arms, and legs	Red and flat, possibly with raised areas; begins on about the 4th day, appearing as body temperature drops suddenly to normal; lasts for a few hours to 2 days
Erythema infectiosum (fifth disease, parvovirus B19 infection)	4 to 14 days	From before the onset of the rash until a few days after	Starts on the cheeks; spreads to the arms, legs, and trunk	Red and flat with raised areas, often blotchy and with lacy patterns; begins shortly after the onset of symptoms; lasts 5 to 10 days; may recur for several weeks
Chickenpox (varicella)	11 to 15 days	From a few days before the onset of symptoms until all spots have crusted	Usually appears first on the face and trunk; later on the neck, arms, legs, and scalp; infrequently on the palms and soles	Small, flat, red sores that become raised and form round, fluid-filled blisters against a red background before finally crusting; appears in crops, so various stages are present simultaneously; begins shortly after the onset of symptoms; lasts a few days to 2 weeks

Enteroviral Infections: Common in Childhood

The enteroviruses include numerous strains of coxsackievirus, echovirus, enterovirus, and poliovirus. These viruses are responsible for illness in 10 to 30 million people each year in the United States, primarily in the summer and fall. Infections are highly contagious and typically affect many people in a community, sometimes reaching epidemic proportions. Enteroviral infections are most common in children, particularly those living in conditions of poor hygiene.

The infection begins when material contaminated with the virus is swallowed. The virus then reproduces in the digestive tract. The body's immune defenses stop many infections at this stage, and the result is few or no symptoms. Colds and upper respiratory infections are common outcomes of infection with enteroviruses. Sometimes, the virus survives and spreads into the bloodstream, resulting in fever, headache, sore throat, and, at times, vomiting. People often refer to such illnesses as the "summer flu," although they are not influenza. Some strains of enterovirus also produce a generalized, nonitchy rash on the skin or sores inside the mouth. This type of illness is by far the most common enteroviral infection. Rarely, an enterovirus will progress from this stage to attack a particular organ. The virus can attack many different organs, and the symptoms and severity of disease depend on the specific organ infected. Several diseases are caused by enteroviruses:

Hand-foot-and-mouth disease affects the skin and mucous membranes, causing painful sores to appear inside the mouth, on the hands and feet, and occasionally on the buttocks or genitals.
Herpangina also affects the skin and mucous membranes, causing painful sores on the tongue and the back of the throat.
Aseptic meningitis affects the membranes covering the brain and spinal cord (meninges), causing severe headache, stiff neck, and sensitivity to light.
Encephalitis affects the brain, causing confusion, weakness, seizures, and coma.
Paralytic poliomyelitis affects the nervous system, causing weakness of various muscles.
Myocarditis affects the heart, causing weakness and shortness of breath with exertion.
Epidemic pleurodynia (Bornholm disease) affects the muscles, causing severe intermittent pain in the wall of the lower chest (adults) or upper abdomen (children).
Hemorrhagic conjunctivitis affects the eyes, causing painful, red, runny eyes; bleeding under the conjunctiva; and swollen eyelids.

Enteroviral infections usually resolve completely, but infections of the heart or central nervous system are occasionally fatal. There is no cure. Treatment is directed at relieving symptoms.

What Is Kawasaki Disease?

Kawasaki disease produces inflammation in the walls of blood vessels throughout the body. The cause is unknown, but evidence suggests a virus or other infectious organism triggers an abnormal immune system response in genetically predisposed children. Inflammation of blood vessels in the heart causes the most serious problems.

Most children with Kawasaki disease range in age from 1 to 8 years, although infants and adolescents can be affected. Roughly twice as many boys as girls are affected. The illness is more common in children of Japanese descent. Several thousand cases of Kawasaki disease are estimated to occur in the United States every year.

The illness begins with fever—usually above 102° F (38.9° C)—which rises and falls over 1 to 3 weeks. Within a day or two, the eyes become red but without any discharge. Within 5 days, a red, patchy rash usually appears over the trunk, around the diaper area, and on mucous membranes, such as the lining of the mouth or vagina. The child has a red throat; reddened, dry, cracked lips; and a strawberry-red tongue. Also, the palms and soles turn red or purplish red, and the hands and feet often swell. The skin on the fingers and toes begins to peel about 10 days after the illness starts. The lymph nodes in the neck are often swollen and slightly tender. The illness may last from 2 to 12 weeks or longer.

About 50% of children develop problems involving the heart, such as a rapid or irregular heart beat, usually beginning 1 to 4 weeks after the onset of illness. Half of the children with heart problems develop the most serious heart problem, coronary artery aneurysm (a bulge in the wall of a coronary artery). These aneurysms can rupture or provoke a blood clot, leading to a heart attack and sudden death. Other problems include inflammation of the tissues lining the brain (meningitis), joints, and gallbladder. These symptoms eventually resolve without causing permanent damage. Doctors perform an ultrasound of the heart to detect coronary artery aneurysms.

Children recover completely if their coronary arteries are not affected within the first 8 weeks of illness. For those with coronary artery problems, survival varies with the severity of disease. With treatment, less than 0.01% of children in the United States with Kawasaki disease die. Without treatment, the death rate may reach 1%. Of those who die, death typically occurs in the first few months but can occur decades afterward. About half of the aneurysms resolve within 1 year. Large aneurysms are less likely to resolve. However, even the ones that resolve may lead to an increased risk of heart problems in adulthood.

Treatment given within 10 days of symptoms significantly reduces the risk of coronary artery damage and speeds the resolution of fever, rash, and discomfort. For 1 to 4 days, high doses of immunoglobulin are given intravenously, and high doses of aspirin are given by mouth. Once the fever is gone, a lower dose of aspirin is usually continued for at least 8 weeks. If there are no coronary artery aneurysms and signs of inflammation are gone, aspirin may be stopped. However, children with coronary artery abnormalities require continuous and long-term treatment with aspirin. An annual flu vaccination is indicated for children (6 months of age or older) receiving long-term treatment with aspirin. If the child contracts influenza or chickenpox, dipyridamole is sometimes used temporarily instead of aspirin to lessen the risk of Reye's syndrome.

Children with large coronary aneurysms may be treated with anticoagulant drugs such as warfarin or dipyridamole. Some children may even require coronary artery bypass grafting or, rarely, a heart transplant.

Last full review/revision May 2007 by Mary T. Caserta, MD