Experts concerned about potential flu pandemic
Experts are clearly extremely concerned about the new swine flu virus which the World Health Organisation warned today has the potential to cause a pandemic.
The virus has killed at least 60 people in Mexico and appears to have infected more than 1,000. The same virus also appears to be behind infections in Texas and California, with suspected cases reportedly being tested in New York.
Dr Alan Hay, director of the World Influenza Centre in London, told me this afternoon that we must take this seriously: "It looks pretty ominous, one has to say. It's difficult to look on the bright side at the moment." He stressed, though, that it's still early days, there's a lot we don't know and he doesn't want to be alarmist.
What's most worrying is that this new virus is affecting young, healthy adults - the same group affected by the pandemic flu virus of 1918. Those usually vulnerable to flu, the elderly and the very young, were at less risk then and, it appears, now.
According to Dr Hay this is key in trying to assess the likelihood of this virus causing a pandemic: "That was the unusual feature about 1918, it was the healthy young adults that suffered most... and I think everybody understands the implications," he said.
He described the situation in Mexico as "totally different" from the intermittent cases of H5N1 bird flu among people, because it appears to be spreading so fast. Sporadic bird flu infections in people have alerted the world to the possibility of a pandemic, but Dr Hay said this H1 swine flu virus is "already worse than H5", in terms of "the number of cases, the number of deaths and the locality of the area affected...This isn't sporadic, this is human".
Dr Hay stressed that it may turn out that the situation is less alarming than it appears now, but this will be hard to assess until experts know clinical details of the cases in Mexico, such as the length of time from infection to death.
Dr Hay's laboratory in north London expects to receive samples from the new cases next week, via the US Centers for Disease Control. His team can then help to advise on the best possible vaccine. Already, his team and others around the world are working on a fast diagnostic test so that labs likely to see new cases can confirm whether or not people have the virus, as soon as possible. Speed will be of the essence in containing infections.
There are eight genes in the flu virus. According to Dr Hay, this new one has six genes from swine flu viruses already known to have been circulating in the US, and two from swine flu viruses from Europe and Asia. The US swine flu virus genes in this new virus are themselves mixtures of swine flu, bird flu and human flu viruses - what's described as a classic "re-assortment" - a combination feared most by those watching for a flu pandemic. Experts around the world have been warning for years that this is inevitable. The last pandemic was in 1968 and killed around a million people worldwide.
The next few days and weeks will be crucial. One possibly hopeful sign is that of the eight cases in the US there has been only one hospitalisation, and no deaths. So it may turn out that there is some other kind of infection at work in Mexico, as well as the new flu virus.