Gastroenteritis. Respiratory Infections. Acute Respiratory Disease of Military Recruits

The incidence of adenovirus gastroenteritis in the world has ranged from 1.5 to 12%. Enteric adenoviruses are second only to rotaviruses as the leading causes of child­hood gastroenteritis. Diarrhea is usually associated with fever and can last for up to 2 weeks. Although diarrhea can occur during infection by any type of adenovirus, Ad40 and Ad41 specifically cause diarrhea.

Adenovirus type 31 (Ad31) is also suspected of causing infantile gastroenteri­tis and, after detailed amino-acid sequence characteriza­tion, has been determined to be closely related to Ad40 and Ad41. Ad31 has been more closely associated with diarrhea than any of the other nonenteric adenoviruses.

Some estimate that Ad40 and Ad41 contribute to 5 to 20% of hospitalizations for diarrhea in developed countries. Children younger than a few years are the most vulnerable to infection.

Respiratory Infections. Adenoviruses, particularly serotypes 1-6, have been shown to contribute to the etiology of acute respiratory diseases (ARDs) throughout the world, especially in chil­dren. It has been estimated through serologic surveys that 10% of all respiratory diseases in children are caused by adenoviruses. Symptoms such as fever, chills, head­ache, malaise, and myalgia are commonly observed during adenovirus respiratory infections.

Secondary transmission in households can be as high as 50% due to fecal-oral transmission from children shed­ding virus in the feces. Adenoviruses can be recovered from the throat or stool of an infected child for up to 3 weeks. Adenovirus respiratory infections are also well documented in adults.

Adenovirus serotypes 1-7 are associated with upper respiratory illnesses such as pharyngitis, tonsillitis, and the common cold. Lower respiratory illnesses due to adenoviruses include bronchitis, bronchiolitis, and pneu­monia, with the latter sometimes resulting in severe (sometimes fatal) illness in infants and children.

Acute Respiratory Disease of Military Recruits. ARD is a respiratory infection characterized by nasal congestion, coryza (nasal discharge), and a cough found simultaneously with fever, chills, malaise, myalgia, and a headache. The disease may progress and become fatal due to pneumonitis. It can be transmitted from person to person, usually under conditions of fatigue and crowding, and was thus initially recognized in military recruits.

Due to the disruption caused by this disease, a commission was organized to define this illness during World War II. Through epidemiologic and human volunteer investiga­tions the disease was termed acute respiratory disease (ARD) and distinguished from other respiratory tract diseases as being caused by a filterable agent and as having an incubation period of 5-6 days.

Vaccines against adenovirus serotypes 4 and 7 became available in 1971 and drastically reduced ARD in military institutions. In 1996, the manufacturer of these vaccines ceased production, resulting in an ARD epidemic in more than 1000 military trainees due to adenovirus type 4. Deaths from adenovirus pneumonia in the military are rare, but do occur. Studies have shown that other sources of risk include college dorms, children’s institutions, and day care facilities.

Pharyngoconjunctival Fever. Pharyngoconjunctival fever (PCF) refers to a syndrome of pharyngitis, conjunctivitis, and spiking fever. Symptoms of this syndrome include unilateral or bilateral conjuncti­vitis, mild throat tenderness, and fevers up to 104 °F. The illness usually lasts from 5-7 days, with no permanent eye damage. Some cases may progress and result in pneumo­nia.

The most commonly isolated adenovirus serotype is 3, although 7 and 14 have also been associated with PCF. The disease is best known for being found around summer camps, pools, and small lakes. Transmission of the agent appears to require direct contact with the water, allowing the virus direct contact with the eyes or upper respiratory tract. Secondary spread is common, although adults con­tracting the disease tend to have milder symptoms, usu­ally only conjunctivitis.