An uncommon, but resurgent and highly virulent strain of the cold virus, called adenovirus type 14 or Ad14, is spreading in the US and is causing severe and sometimes fatal respiratory illness, even in healthy adults.

The virus has killed 10 people since May last year, when a 12 day old baby girl died from it in New York City. Between March and June 2007, there have been 140 confirmed cases of Ad14 in Oregon, Texas and Washington, according to the US Centers for Disease Control and Prevention (CDC).

53 of the patients (38 per cent) had to be hospitalized, 24 of whom were admitted to intensive care, of whom 9 patients died.

The CDC said that the strain of Ad14 in all four states were genetically identical, but different to the one that spread in 1955, suggesting this is a new strain of an old virus. They have not found any link between the New York case and the outbreaks in the other four states.

Also, an investigation by the New York City Department of Health and Mental Hygiene has not found any other cases of Ad14 illnesses in the area.

Investigations have been carried out by state and city health officials, the CDC and the US Air Force. The CDC’s Morbidity and Mortality Weekly Report (MMWR) for 16th November summarizes their findings.

The CDC warns that state and local health professionals should be alert to the possibility that this virus will cause further outbreaks.

In Oregon the cases were first noticed when a hospital doctor reported several patients admitted with severe pneuomonia between early March and early April 2007. 15 of the 17 patients were confirmed by lab tests done by the CDC as being infected with Ad14.

Investigations by Oregon state health officials traced 68 people who tested positive for adenovirus between 1st November 2006 and 30th April 2007. Of these, 50 were available for further tests, from which there emerged 31 cases of Ad14, of which 30 were reviewed further. Of the 30 patients, 22 were male, and the age range was 2 weeks to 82 years. 7 (23 per cent) died from severe pneumonia.

The authorities were not able to establish a link in the hospitals or the community to explain how Ad14 was spread among the patients.

In Washington, the case of four residents in a residential care facility was brought to the attention of state health officials in mid-May this year. They were in hospital suffering from pneumonia of unknown origin. The patients, three of whom were female, were aged between 40 and 62, and all four smoked. One had AIDS and the others had chronic obstructive pulmonary disease.

The initial symptoms were cough, fever, shortness of breath, and they started towards the end of April. Three patients required intensive care and assisted breathing for severe pneumonia. The patient with AIDS died and the others recovered. Three of the patients were confirmed by the CDC as having been infected with Ad14 (isolate was not available for the fourth). No other cases of Ad14 were identified at the residential home.

In Texas, during an investigation conducted between February and June this year, over 100 cases of Ad14 were found among 423 cases of respiratory illness among military trainees at Lackland Air Force Base (LAFB). Before this outbreak there was one case in May last year on the base.

A total of 27 patients were admitted to hospital with pneumonia, 5 of whom had to have intensive care. One patient died. Of the 16 for whom throat swabs were collected, including the 5 in intensive care, all tested positive for Ad14. Of 218 healthcare workers who worked at the hospitals the Ad14 patients had been treated at, six tested positive for Ad14, five of whom had had direct contact with the infected patients.

Adenoviruses were first identified in the 1950s and cause a broad range of conditions from conjunctivitis, upper respiratory illness, through pneumonia, and gastrointestinal disease. They usually infect vulnerable patients such as the very young or the very old, or those with underlying medical conditions.

It is unusual for adenoviruses to cause hospitalization, and it is rare for healthy people to die from them.

Ad14 appears to be resurging in the US, after lying low for some 50 or so years. An outbreak occurred among military recruits in Europe in 1969, and more recently, in 2001-2002, Ad14 was linked to an outbreak of respiratory adenoviral infections in the pediatric ward of a Taiwan hospital.

“Acute Respiratory Disease Associated with Adenovirus Serotype 14; Four States, 2006 – 2007.”
US Centers for Disease Control and Prevention: Morbidity and Mortality Weekly Report (MMWR).
November 16, 2007 / 56(45);1181-1184.

Full MMWR report.

Written by: Catharine Paddock