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Despite New Ad14 Bug's Fatal Potential, Most Get Mild Illness
Daniel J. DeNoon
WebMD Health News
Reviewed By Louise Chang, MD
Nov. 20, 2007 -- It's been deadly for 10 Americans -- but most people who catch the new strain of Ad14 "killer cold virus" get only a mild illness, the CDC says.
Here's the main thing the federal health agency wants you to know: The new strain of Ad14 certainly can cause very serious disease. But it's not nearly as deadly as other bugs that circulate every winter.
Nobody knows how many more people will die from Ad14 this year -- if any. But the number is sure to be vastly smaller than the average year's toll of 36,000 deaths from flu and 11,000 deaths from respiratory syncytial virus (RSV).
What do we need to know about the new virus this winter? WebMD spoke with the CDC's Larry J. Anderson, MD, chief of the division of viral and rickettsial diseases, National Center for Infectious Diseases.
What are the symptoms of infection with the new Ad14 virus?
Anderson: "First, people should know that this is one of the adenoviruses, which can cause a wide range of things. Probably the most common is respiratory illness. This means there is a kind of layering of symptoms. First there are the symptoms of a common cold, but possibly with a fever: runny nose, sore throat, and cough. Then there may be the more severe symptoms of lower respiratory involvement: productive cough, shortness of breath.
"Almost all the 51 types of adenovirus can cause the full range of symptoms -- and so can rhinovirus, a different cold virus. What is unusual about Ad14 is the severity of symptoms. It is not that the other adenoviruses can't do this, they just don't do it this often."
Does everyone who catches Ad14 get a serious illness?
Anderson: "In the outbreak at Lackland Air Force Base, the vast majority of individuals infected with Ad14 had the more mild end of the spectrum of illness. They tended to have fever with cold, but only the minority of individuals were hospitalized. In our preliminary analysis of data from an investigation looking at recruits over the course of the six and a half weeks of military training, a little over 150 or 160 people -- about half -- got infected with Ad14. Maybe 5% had no symptoms, but nobody was hospitalized in that group.
"That is reassuring. And if you think about the epidemic in Oregon, we saw that the cases were not linked to one another. That means the virus had to have spread out in a variety of places. A lot of other people must have been infected for it to spread that broadly. This means that many people were infected that weren't all that ill."
With Ad14 possibly circulating this winter, is there anything people should do when they come down with a cold or flu-like illness?
Anderson: "Do what you usually do. Ad14 really should not change the way you look at respiratory illness this season at all. If you think about relative risk, flu regularly causes more than 30,000 deaths. RSV is a much greater risk in the young child. And rhinoviruses are likely to cause a lot more disease than Ad14. That's because this is an uncommon infection, and the more common infections will be much more of a problem.
"Now here's what you can do. Get your flu vaccination. Get your pneumococcal vaccination. And observe good hygiene -- this means frequent hand washing, and covering your mouth whenever you cough or sneeze."
Let's say my spouse or my child gets cold or flu symptoms. When is it time to call a doctor?
Anderson: "The things to watch out for are persistent fever, a fever that keeps getting higher, or any trouble breathing. It is a matter of symptoms getting more severe -- and when you reach the point of needing medical attention depends on the age and underlying physical condition of the person who is ill."
The earliest victim of this new virus was a baby. What's the message to parents in terms of watching a child with a runny nose or a cold?
Anderson: "Small children always have a runny nose. And there is a whole host of things that can become more severe in the infant; Ad14 is just one of those. Particularly in a young infant, the criteria that you use to decide whether to check with a doctor are different in different situations. For example, in this New York child that died, lethargy and poor feeding were an indication of a more severe illness.
"Really, it is hard to tell. But a mother knows when her child is sick. If you think your child is sick, consult a doctor. It does no harm for a new mother who is not experienced just to call a doctor when she's not sure, just to check in."
How can you know if you have an Ad14 infection?
Anderson: "If you have a serious case of pneumonia, it could be Ad14. Then your doctor should check with the local health department. Ad14 needs to be included in the list of possible causes of severe pneumonia -- but it is not the situation where you have a test and are scared because it's Ad14. Because if you had Ad14 and a cold, you would not do anything different unless you got sicker. So you treat and monitor a flu-like illness based on the severity of clinical symptoms. Suspecting that is it Ad14 doesn't tell you your illness is bad. But if it is bad, your doctor may suspect Ad14 as one of several possible causes."
Is there any particular treatment for Ad14 illness?
Anderson: "There is no antiviral drug licensed or known to be effective for adenovirus infections. Treatment is specific to the symptoms. If a person is having trouble breathing, that patient may be intubated in really severe cases."
Who is most at risk of Ad14 infection and severe illness?
Anderson: "Adenoviruses have been a problem for military recruits for a long time. Ad3, Ad4, Ad7, sometimes Ad21, now Ad14. That appears to be a problem because of crowding together in open-floor dorms, and it is possibly related to stress and physical exertion. But this has been going on for a long time.
"Otherwise we don't know a lot about Ad14. We have not been watching it that long. What we do know, if we look at the individuals that had more severe disease, it is the young infant and the older patient. Infants are at risk of a number of infections because they are small, they have immature immune systems, and they are not as good as adults are at fighting off infections. But non-military cases were in older patients. So this gets down to the same groups that would be at risk for flu or other respiratory pathogens.
"The real message is that clinician and public-health folks, when they thinking about patients with pneumonia for which they don't know the cause, to keep Ad14 on the suspect list of pathogens that may be causing the illness. This is important not so much for the individual person as for public health measures."
Does the CDC expect Ad14 to become a bigger public health problem?
Anderson: "We don't know if it is going to be a bigger problem. We had this cluster in Oregon, which for the broader public health community is the one that stands out. But we have not had reports of other clusters of cases like this. This probably means there have not been any other major clusters of cases. One reason we put out the MMWR report is to alert public health officials so we can see whether this is a wider problem. That we have not heard anything more suggests it is not a major public health problem like flu or RSV.
"So is Ad14 something I should be alarmed about? The answer is no. Doctors should keep it in mind when making a diagnosis, but there is nothing different for people to do."
SOURCES: Larry J. Anderson, MD, branch chief, division of viral and rickettsial diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta. CDC, Morbidity and Mortality Weekly Report, Nov. 16, 2007; vol 56: pp 1181-1184.
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