Disease and Treatment

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Disease:

About 5% of acute respiratory disease in children is due to adenovirus infection. Adenovirus 1, 2 and 5 are the most common serotypes in humans, in fact, over half of children present antibodies against at least one of these three. In adults, adenovirus infections are responsible for an estimated 3% of cases of respiratory disease. 

Severe disease from adenovirus is most commonly associated with Ad7, a member of the subgroup Human adenovirus B, as well as Ad3 and Ad4. These three serotypes have a history of presentation in military recruits, causing epidemics with close to 80% infection rates in a single unit of recruits, resulting in the hospitalization of 20-40%. The crowding together of large numbers of young men from a variety of backgrounds in a stressful environment has been suggested as the most likely cause for the high incidence of acute adenovirus infections in this population. 

Ad7 is estimated to be the agent of about 20% of all cases of adenovirus reported to the World Health Organization. Strains 40 and 41, in the sub-group Human adenovirus F, are most commonly associated with gastrointestinal infection and intestinal tract infections, most common in infants and children under the age of 5. Other sub-families with serotypes associcated with enteritis include Human adenovirus A, B, D and E. Serotype 35 is also noted to cause pneumonia in the elderly and immuno-compromised.

Seasonal Variation is a characteristic of adenovirus infection. Adenoviral respiratory infections are more common in the late winter months and spring and even into early summer. Gastrointestinal infections; however, are not associated with any specific season variation.

Transmission:

Adenoviruses are transmitted by both respiratory and fecal-oral routes:

Respiratory Transmission occurs by making contact with infectious viral material either directly from an individual or from anything with which an infected individual might have interacted. Secretions from the respiratory tract can contain the virus and adenoviruses are able to survive away from humans for many hours. Common sites of frequent adenovirus transmission include daycare centers, as children are particularly susceptible. 

Intestinal Tract Transmission most commonly through fecal-oral contact, such as contaminated food and water or someone not washing their hands well after going to the bathroom. As the virus can shed for many months after primary infection particularly through stool, infected children often spread the infection to siblings and other household inhabitants.

Symptoms:

Below is a chart of common symptoms associated with adenovirus infection:

Chart Image courtesy of University of Virginia

Specific symptoms resulting from respiratory acquired adenovirus infection include the following: 

  • respiratory illness
  • the common cold
  • conjunctivitis 
  • croup (or viral laryngotracheobronchitis)
  • bronchitis
  • pneumonia 

Complications:

In general complications associated with even acute adenovirus are rare. Immuno-compromised individuals, particuarly children, tend to be at higher risk for the development of more severe adenoviral infections. The development of pneumonia has been noted to result in chronic  lung disease; however this is highly uncommon.  Finally, a rare but severe complication of intestinal adenovirus is intussusception. This disorder is constituted by a blockage of the intestine such that part of the intestine slides over another section. It is a very serious condition most commonly seen in infants. Associated symptoms include vomiting, weakness, bloody stool, swelling of the abdomen, severe pain and the knees of the infant being tightly drawn to the chest.  

Treatment:

Treatment for adenovirus infection is generally limited to supportive therapies and there is no specific cure. For acute respiratory infections, bronchodilator medications can by used to maintain open airways, as well as supplemental oxygen and, in very severe cases resulting in respiratory failure,  mechanical ventilation. Treatment for gastrointestinal infection includes oral re-hydration therapy and in more severe cases, intravenous fluids or nasogastric tube feeding. 

In immuno-compromised individuals, several therapies have been experiment with for treating adenoviral infection. For example, in bone marrow transplant patients,  Ribavirin, Ganciclovir and even Cidofovir  have both been used; however, none has proved to be of particular use.