Common adenovirus has many subtypes

ASK THE DOCTORS By Robert Ashley, M.D.

Dear Doctor: I’ve been hearing about adenovirus, which is often mistaken as the flu. How can you tell the difference? And is it as serious as the flu?

Dear Reader: Your question is a great reminder, especially during flu season, of how complex and ubiquitous viruses are. They cause a host of illnesses, with the common cold alone blamed on more than 200 identified subtypes of virus and many more that are still unidentified. One main group of viruses is adenovirus.

Adenovirus got its name because it was first isolated in the adenoids, although this isn’t the only place it’s found. More than 60 types of adenovirus exist, with some causing much different symptoms than others. Serotypes 3, 5, 7, 14 and 21, for example, have been associated with more severe disease.

Adenoviruses most commonly cause upper respiratory symptoms. These include inflammation of the throat, leading to a sore throat, and swelling of the membranes in the nose, leading to runny nose and nasal congestion. Such symptoms are often accompanied by headache, fever, fatigue, muscle pain and stomach pain.

But adenovirus can also lead to conjunctivitis, laryngitis, bronchitis and even pneumonia. Adenovirus-caused pneumonia more often affects those younger than 5 years old, accounting for 15 percent of pneumonias in this age group. Young children can also be affected by subtypes of adenovirus that lead to diarrhea, which can last up to eight to 12 days.

In rare cases, the virus can affect the brain, causing meningitis or encephalitis, or lead to inflammation of the liver and the heart muscle. In people with a compromised immune system or those who have had an organ transplant, adenovirus can lead to more severe disease and possible death.

Adenovirus is a resilient virus. It can survive for long periods on environmental surfaces and — though bleach, formaldehyde and heat can inactivate it — the virus is resistant to many disinfectants. It can be transmitted through respiratory droplets spread by sneezing, coughing or contact with secretions. Adenovirus is also shed in the stool for many weeks after an acute infection. Without proper handwashing by all parties, the virus can then be taken in orally by another individual.

Because adenovirus is easily transmissible, it’s associated with outbreaks of infection in day care settings and among military recruits. In fact, military recruits are now vaccinated against adenovirus, which has decreased their rate of infection.

Adenovirus is diagnosed by either viral culture or by tests producing more rapid results. The treatment is similar to those for other cold viruses — fluid intake, rest, acetaminophen or nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen) for headache and medications for diarrhea. For people who are taking drugs to suppress the immune system, the antiviral medication cidofovir can improve survival.

Yes, many of the symptoms are similar to influenza, especially in young children. The fever in those under 5 with adenovirus averages 102.6 degrees. This is similar to influenza. However, influenza is a much deadlier virus, especially among older individuals, causing thousands of deaths per year. Although adenovirus can cause significant illness, it doesn’t usually lead to the intensity of sickness and the death rates seen with flu.

Rapid flu tests can help distinguish whether a specific illness is due to influenza or another virus, such as adenovirus, but the point remains: If a person becomes dehydrated or if his or her mental state changes, seek emergency help. Neither illness should be taken lightly.

Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.