New bird flu strain: Little evidence of global threat so far

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Chinese health workers collect bags of dead chickens at Huhuai wholesale agricultural market in Shanghai on Friday. Authorities in Shanghai began the mass slaughter of poultry at a market after the H7N9 bird flu virus, which has killed five people in China, was detected there, state media said.

By Robert Bazell, Chief Science and Health Correspondent

Could the recent outbreak of illnesses or death from a new strain of bird flu be the beginning of the next pandemic? Were I a betting man, I'd say the odds are against it. The world is far better prepared and aware than it was even just a few years ago. But because of that greater vigilance, we know there is a potential threat from the H7N9 virus that has now killed?six people and infected 14, so far all in China. No responsible scientist would discount it.

As the World Health Organization?s FAQs on H7N9 phrases it, ?Any animal influenza virus that develops the ability to infect people is a theoretical risk to cause a pandemic. However, whether the influenza A(H7N9) virus could actually cause a pandemic is unknown.??

All flu viruses pass among many species, especially birds, pigs and humans. They come in many strains, and they mutate frequently. The big danger is a new one that would be both deadly to humans and to which humans have no immunity.?The Spanish flu of 1918, for example, which mutated as it jumped between pigs and people, killed an estimated 20 to 40 million people worldwide.

The new strain is different from H5N1 avian influenza, which has killed 371 people out of 622 infected in 15 countries since 2003.

One of the most frightening aspects of this latest outbreak is that it is occurring suddenly over thousands of square miles in China. A Chinese blogger put together this map of the cases up to Thursday morning. The University of Minnesota?s Center for Infectious Disease Research and Policy translated the map and checked out the information.

?It is very alarming to have so many cases appear so suddenly over such a wide area,? the center?s director, Dr. Michael Osterholm, told NBC News.?

Another cause for concern: No one knows where the deadly virus is coming from. The guess is chickens.?Similar H7N9 viruses occur in birds, including chickens in China, the United States and throughout the world. But with modern genetic technology scientists can identify strains precisely. On Thursday, Chinese officials said they had found the virus in a pigeon near a Shanghai market.?If the virus is being spread by chickens or pigeons, it is does not appear to make them sick, so culling sick animals might be a very difficult path to containment.

So far, it appears that the virus doesn't spread easily among people. The WHO has said that more than 400 close contacts of confirmed cases are being closely monitored, with no evidence of person-to-person spread. However, there were reports by the official Chinese news agency Xinhuan late Thursday that one person who'd had contact with a dead victim was showing flu symptoms including fever, running nose and itching throat.?If numbers continue to increase the new virus could remain a public health menace, but if people don?t catch it from one another it can never be a pandemic.

The controversial recent research on ?killer flu viruses? has now been vindicated, experts say, because it showed just what genes need to change to allow person to person transmission. ?So far, the new virus lacks the genes it needs to spread among people.? But experts warn the more viruses circulate, the greater chances for a mutation that will allow for spread among humans.

The global health community has begun discussions about making a vaccine, and the U.S. Centers for Disease Control and Prevention announced on Thursday plans to start preparing a vaccine, just in case. ?The CDC has also developed a diagnostic test for H7N9 and is submitting it to the Food and Drug Administration for approval, a spokeswoman said. The tests might be available shortly, but a vaccine would likely not be widely available for months.?Tests have found that the virus is sensitive to Tamiflu and other anti-influenza medications which many nations have stockpiled. Let?s hope they are not needed.

Related:

WHO: No sign of 'sustained' bird flu spread between humans

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