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Last week, the Centers for Disease Control and Prevention (CDC) reported that a new virulent strain of the common cold virus, adenovirus, has caused 10 deaths over the last 18 months . The virus, identified as adenovirus serotype 14 (Ad14), is a rarely reported strain of adenovirus that can cause severe and even fatal respiratory illness. It’s unusual since adenoviruses typically cause non-lethal infections. According the the CDC report:
The cases described in this report are unusual because they suggest the emergence of a new and virulent Ad14 variant that has spread within the United States.
Indeed, between the months of March-June 2007, Ad14 caused at least 140 respiratory illnesses in three states; Oregon, Texas and Washington . More than 50 of those patients were hospitalized, including 24 who were admitted to intensive care units. Nine of those patients died, most from severe pneumonia. People of all ages have been affected, including healthy young adults, typically the group least susceptible.
Adenoviruses are a group of viruses, specifically non-enveloped icosahedral DNA viruses, that infect various tissues, including respiratory, gastrointestinal and urinary tracts as well as the eye. Adenoviruses get their name as they were originally isolated from human adenoid tissue (tonsils) in the 1950’s [2-3]. Adenoviruses comprise more than 50 serotypes (meaning a group of organisms that can be distinguished based on molecules present on their cell surface that are able to stimulate an immune response), clustered in 6 species designated A through F.
Adenoviruses display a certain degree of tissue specificity and several clinical symptoms are associated with particular groups of virus. For example, adenovirus serotypes Ad2 and Ad5 from species C are associated with approximately 7% of respiratory illnesses in children . In contrast, Ad40 and Ad41 from species F are typically associated with gastrointestinal infection. Adenovirus serotypes 8, 19 and 37 are associated with a relatively severe contagious form of epidemic keratoconjunctivitis (inflammation of the cornea and conjunctiva, the outermost layer of the eye and inner surface of the eyelids).
Ad14 infection was first described in 1955  and was associated with epidemic acute respiratory disease in military recruits in Europe in 1969  but has since been detected infrequently.
Transmission and symptoms
Adenoviruses are typically transmitted via aerosolized secretions from the respiratory tract. Infection can also occur from contact with infectious material on inanimate objects, such as doorknobs and drinking fountains. The gastrointestinal strain is usually transmitted by fecal-oral contact, occurring from poor hand washing or ingestion of contaminated food or water.
Most adenovirus infections affect the upper respiratory tract, often presenting as tonsillitis, conjunctivitis, ear infection and croup (a respiratory disease causing inflammation of the larynx and upper airway in infants and young children). Children may develop bronchiolitis (an inflammation of the bronchioles, the smallest air passages of the lungs) or pneumonia. Pneumonia results in the alveoli (tiny air-filled sacs in the lung that are responsible for absorbing oxygen) becoming inflamed and filled with fluid. Adenoviruses can also cause stomach flu (gastroenteritis).
Adenoviral respiratory infections are most common in the late winter, spring and early summer, while intestinal tract infections occur throughout the year. In most people, adenovirus infection is asymptomatic. For people who do experience symptoms, there are no specific antiviral treatments and symptoms often gradually disappear on their own.
Some of the most common symptoms of adenoviral infections include:
Respiratory infections, with symptoms developing 2 to 14 days after exposure
- runny nose
- sore throat
- severe cough
- swollen lymph nodes
- abrupt onset of watery diarrhea
- abdominal tenderness
Intestinal tract infections, with symptoms developing 3 to 10 days after exposure and lasting 1 to 2 weeks (usually occurring in children < 4 years)
There is no cure for adenovirus infection and, because the infection is caused by a virus, antibiotics are not effective. Treatment is focused on relieving symptoms associated with infection and include increased fluid intake, pain relievers and plenty of rest.
In the case of Ad14, a number of antiviral drugs have been used to treat infection, including ribavirin, vibarabine and cidofovir, but none have been shown to be effective . Patients have been treated with liquids, pain relievers and bed rest. Retrospective examination of laboratory reports showed that the virus has been responsible for a number of respiratory diseases, including pneumonia, febrile respiratory infection and conjunctivitis. Although scientists have not determined the prevalence of Ad14 in the population, they emphasize that the virus is not widespread.
Clinicians with questions related to testing of patients for adenovirus or Ad14 infection have been advised to contact their state health departments. CDC officials don’t consider the Ad14 outbreak to be a cause for alarm and are not recommending any new precautions for the the general public.
Acute Respiratory Disease Associated with Adenovirus Serotype 14 — Four States, 2006–2007. Centers for Disease Control and Prevention (CDC). MMWR Morb Mortal Wkly Rep. 2007 Nov 16;56(45):1181-1184.
Rowe et al. Isolation of a cytopathogenic agent from human adenoids undergoing spontaneous degeneration in tissue culture. Proc Soc Exp Biol Med. 1953 Dec;84(3):570-3.
Hilleman and Werner. Recovery of new agent from patients with acute respiratory illness. Proc Soc Exp Biol Med. 1954 Jan;85(1):183-8.
Sinaniotis CA. Viral pneumoniae in children: incidence and aetiology. Paediatr Respir Rev. 2004;5 Suppl A:S197-200.
Van der Veen et al. Isolation and typing of adenoviruses recovered from military recruits with acute respiratory disease in The Netherlands. Am J Hyg. 1957 Mar;65(2):119-29.
Hierholzer and Pumarola. Antigenic characterization of intermediate adenovirus 14-11 strains associated with upper respiratory illness in a military camp. Infect Immun. 1976 Feb;13(2):354-9.
- Adenovirus. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and practice of infectious disease. 6th edition. Philadelphia, PA: Churchill Livingstone; 2004.