Looking for a quick rundown of basic information about the new strain of bird flu that's infecting people in China? The Toronto Star's Jennifer Yang has a great, one-page breakdown that will get you caught up on just about everything you need to know
— including how scared you should be. For the record, the answer to that is complicated. We aren't near a pandemic yet. But we do need to get a better handle on understanding how this virus works so we can stop it from spreading. It's a serious situation and the news is not all good news. But we don't seem to be at a point where anybody outside of China and the international public health community should be in an urgent crisis mode. — Maggie
If you've been following news about the H7N9 bird flu outbreak in China, it may be relieving to know that doctors are now looking for (and finding) people who are infected with the virus, but who appear perfectly healthy
or who are just suffering from a mild case of the yucks. It's an important reminder that we identify new diseases when sick people show up, very sick, in hospitals. Just because those are the only people we know to have the disease, doesn't mean the disease makes EVERYONE that sick. Hidden in the background are often many, many people who shrug off a new flu the same way you or I have shrugged off an old, boring flu. This is context you should take into reading about every new disease. — Maggie
The Centers for Disease Control and Prevention, and the World Health Organization, say that H5N1 bird flu kills some 60% of the human beings it manages to infect. Basically, it hasn't infected many people—because it can't be spread from person to person—but most of the people it does infect die.
But this might not be the full story.
After I posted a summary of the current controversies surrounding H5N1 research, I got an interesting email from Vincent Racaniello, a professor of microbiology at Columbia University Medical Center. Racaniello points out that the 60% death rate statistics are based on people who show up at hospitals with serious symptoms of infection. So far, there've only been about 600 cases. And, yes, about 60% of them have died.
However, they don't necessarily represent everybody who has contracted H5N1.
A death rate is only as good as statistics on the rate of infection. If you've got an inaccurate count of the number of people infected, your death rate is going to be wrong. And there's some evidence that might be the case with H5N1.
In a recent study of rural Thai villagers, sera from 800 individuals were collected and analyzed for antibodies against several avian influenza viruses, including H5N1, by hemagglutination-inhibition and neutralization assays. The results indicate that 73 participants (9.1%) had antibody titers against one of two different H5N1 strains. The authors conclude that ‘people in rural central Thailand may have experienced subclinical avian influenza virus infections’. A subclinical infection is one without apparent signs of illness.
If 9% of the rural Asian population has been subclinically infected with avian H5N1 influenza virus strains, it would dramatically change our view of the pathogenicity of the virus. Extensive serological studies must be done to determine the extent of human infection with avian H5N1 influenza viruses. Until we know how many individuals are infected with avian influenza H5N1, we must refrain from making dire conclusions about the pathogenicity of the virus.
I’ve been following the story about the scientists who have been working to figure out how H5N1 bird flu might become transmissible from human to human, the controversial research they used to study that question, and the federal recommendations that are now threatening to keep that research under wraps.
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