Nov. 15, 2007 -- A virulent new form of an old cold virus is spreading in the U.S., causing severe pneumonia and death even in healthy adults.
The virus is adenovirus type 14 or Ad14. Since May 2006, when it killed a 12-day-old girl in New York City, there have been 10 deaths among 141 confirmed cases. Except for the infant girl, the cases came in outbreaks in Oregon, Washington, and Texas.
Different adenovirus strains have caused outbreaks in the past. But this seems to be a particularly "challenging" virus, says CDC epidemic intelligence officer John Su, MD, PhD.
"This particular [adenovirus] is unusual in that it can cause very severe illness in healthy young adults with no other medical condition. That is why this adenovirus stands out from the crowd," Su tells WebMD.
Adenovirus expert Gregory C. Gray, MD, MPH, director of the Center for Emerging Infectious Diseases at the University of Iowa, says particularly virulent strains of adenovirus pop up from time to time.
"I think this Ad14 strain is a matter of concern," Gray tells WebMD. "Something makes this unique. The question is what makes it cause outbreaks of severe disease. It's a bit of a mystery."
U.S. Ad14 Outbreaks
The CDC, in the Nov. 16 issue of Morbidity and Mortality Weekly Report, chronicles the four known Ad14 outbreaks.
New York City, May 2006: An infant girl born after normal pregnancy and delivery had some weight loss three days after birth, but seemed healthy. Over the next week, her physical activity and feeding dropped off. At age 12 days, she was found dead in her bed. A postmortem exam showed she'd had a deep lung infection with Ad14, resulting in acute respiratory distress syndrome.
Oregon, April 2007: A doctor reported that an unusually large number of patients had been showing up at the same hospital with severe pneumonia. A state health department investigation found that Ad14 was responsible for the majority of cases involving adenovirus infections.
Investigators found 30 people infected with Ad14. Five of the cases were in children under age 5; the rest were in people over 18. Twenty-two of the patients had to be hospitalized, 16 of them in the intensive care unit. Seven of these people -- 23% -- died of severe pneumonia.
In contrast, there were no deaths or ICU admissions among people infected with other adenovirus strains.
Washington State, May 2007: Four residents aged 40-62 of the same unit of a residential-care facility were hospitalized for pneumonia. One of these patients had AIDS; the other three had chronic pulmonary obstructive disease ( COPD). Three of the patients required mechanical ventilation. After eight days in the hospital, the patient with AIDS died. The others recovered. All four patients tested positive for adenovirus. Three of the isolates were further tested; all three were Ad14.
Texas, February 2007: Beginning last February, recruits undergoing basic military training at Lackland Air Force Base started coming down with adenovirus infections. From February through June, 90% of analyzed virus isolates were Ad14.
During this time, 27 of these previously healthy young adults were hospitalized for pneumonia. Five went to the ICU. One died. Throat swabs were taken from 16 of these patients, including all five ICU patients. All tested positive for Ad14.
Investigators tested 218 health care workers from the hospital units that treated the recruits; six were positive for Ad14. Five of the six had treated hospitalized Ad14 patients.
The base continued to have a high rate of respiratory illness, with 55 cases from Sept. 23-29, the last week for which test results are available.
An additional 220 cases of Ad14 infection turned up during tests at other Texas military bases that received Lackland recruits. Ad14 was also found in an eye culture from an outpatient in the surrounding community who was treated for pinkeye.
Is it likely that Ad14 has spread beyond these four states? Without hard data, Su is reluctant to speculate, but he suggests that doctors across the U.S. should pay special attention to patients who have severe or worsening colds.
"It is a germ that bears watching," Su says. "People have to be aware of this virus. It is becoming more common, and it does have the capability to cause severe illness in people of all ages. What puts people at risk of severe respiratory infection from Ad14 is not something we clearly understand yet."
Adenovirus Spreads Easily
There are 51 different adenovirus strains. In the 1960s, Gray says, adenovirus was considered a "rather innocuous childhood problem." That opinion changed when adenoviruses turned out to be responsible for huge outbreaks that caused severe disease and deaths among military recruits.
"Now we know adenovirus is really a big player and associated with chronic diseases," Gray says. "The latest condition to be associated with adenovirus is obesity. It's also implicated in heart infections, brain infections, and in some inflammatory diseases of the lung. It is a very interesting virus."
Adenovirus can spread from person to person via aerosolized droplets in sneezes and coughs. But it's also present in feces, and fecal-oral spread is common among young children. The virus can survive for weeks on contaminated surfaces. In the summer, there may be swimming-pool-related outbreaks.
The adenovirus incubation period is two to nine days. Different adenovirus strains behave differently, but outbreaks can be explosive.
A vaccine that protected against the Ad4 and Ad7 adenovirus strains nearly eliminated the U.S. military problem. But when its single manufacturer stopped making the vaccine, serious adenovirus outbreaks once again began to plague recruits.
A new Ad4/Ad7 vaccine is in the works. But Gray says it's unlikely the vaccine will cross-protect against the new Ad14 virus.
Su says it's impossible to tell whether Ad14 will become a major epidemic. But Gray notes that adenovirus disease is more common in the winter months in the U.S. And since there are few labs that can rapidly identify adenovirus infection, it's going to be hard to know exactly how many Ad14 cases occur.
"It could very well increase this winter among some populations, but it will be hard to make an assessment," Gray says.
One thing is known for sure: The new Ad14 virus is very different from the Ad14 strain first discovered in the 1950s.
"The Ad14 strain we see here is genetically distinct from previous strains," Su says. "It is a variant of the virus never seen before."
What to Do About Ad14
What can you do about Ad14?
Parents, Su says, should watch kids' colds carefully. Any child with a severe cold should be taken to a doctor or nurse.
For that matter, anyone with a severe cold or a cold that keeps getting worse should seek medical attention.
"If health care providers see a patient with worsening symptoms like cough or runny nose or troubled breathing, they should send off a sample for testing," Su says. "If it is adenovirus, they should keep daily tabs on that patient until they turn the corner. That way, if they go downhill really fast -- which patients with Ad14 infection can do -- they can get the more intensive medical care they may need."