As new cases of swine flu emerge around the globe, from Ohio to Nova Scotia to New Zealand, the declaration of a "public health emergency" in the United States has further stoked fears and confusion.
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NBC Chief Science and Health Correspondent Robert Bazell answers questions on the outbreak.
If this disease is like a mild flu, why is this being called a public health emergency? And why are officials in the United States concerned?
It's about the potential. It's not about what's happening right now. None of the 40 cases so far in the United States have been very serious. But the virus here is genetically identical to the strain of the virus that is killing people in Mexico.
This is a new virus so there's no natural immunity. It has the potential to spread very widely. That's what raises worries about a possible pandemic.
Don't thousands of people die from the regular flu? What's special this time around?
Generally, people who die from influenza are older people or those who already have respiratory problems. They end up dying of pneumonia. But this time around, the people who died in Mexico are younger. They are apparently healthy people in their 20s, 30s and 40s. That's a big deal. When a virus seems to preferentially affect healthy people, it suggests its a new virus and is causing an overreaction of the immune response. That's what happened with bird flu as well.
Influenza is virus that is always circulating between birds and pigs and people. Some have different genes that make them more or less infectious.
I have symptoms of the flu but haven’t recently been to Mexico? Should I go to the doctor?
You should go to the doctor if you have a fever or are really sick, for instance if you have difficulty breathing, even if you haven't been to Mexico.
The cases in the U.S. are not just among people who have been to Mexico. And the cases in the U.S. are so geographically dispersed and with no obvious connection to each other, that it seems this virus has already spread widely in the United States.
We shouldn’t start overwhelming emergency rooms or doctors' offices with every little sniffle or cough. But fever is the main thing. If you had the flu bad enough to start endangering you, you would feel so awful you would want to go to the doctor anyway.
You should also follow flu etiquette. If you are sick, you should stay home from work or school and limit contact with others.
Why is the disease so much more serious in Mexico than here?
Probably because it started in Mexico. That's going to become a big issue over time. There's supposed to be a pandemic prevention plan to contain a new flu virus by giving people in surrounding area Tamiflu. But it has obviously been spreading in Mexico for up to a month. The new strain of swine flu was discovered in California before the U.S. even knew about cases in Mexico. The virus could also be mutating.
Why is there so much uncertainty about what happens next?
Every epidemic has its own behavior. There's really no way of predicting. This could really just fade out or it could become very serious. Right now we are in a period of great uncertainty. In public health, that's the hardest thing.
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