The evolving Swine Flu story

This afternoon CDC held a "media availability" on the evolving swine flu cases. Evolving is an understatement. There are now more recognized cases, although not all cases are "new," with some cases retrospectively recognized now that more intense investigation is occurring. The total is now seven cases. Two occurred in San Antonio, Texas, two sixteen year old boys in the same school. Three more were found in California (in addition to the initial two cases), including a father - daughter pair. All California cases are in San Diego and neighboring Imperial counties, the location of the initial cases. Those counties are also where there has been the most intense looking. CDC expects more cases to be recognized with the ramped up index of suspicion. They promise to update the situation daily at 3 pm on its website. None of the cases gives a history of contact with pigs, so together with the two "doubles" (the schoolmates and family pair), this strongly suggests active person to person spread. Moreover, the initial two viruses have been completely sequenced and are very similar. Partial information on some of the additional viruses from California are also similar, which reinforces the idea that the virus is in active circulation. How widely we don't yet know. But this isn't all the news.

It turns out this virus is highly unusual, a quadruple reassortant. The genes of a flu virus are packaged in eight discrete segments. When two flu viruses infect the same host cell, the segments of each are copied and repackaged, 8 at a time, in new viral particles which then bud off from the infected cell. They then may infect a new host cell. In this repackaging process the segments of the two different viruses may mix and match, so that new virus particle will have segments from two different viruses. The new virus is, in a sense, not just a swine flu virus. It does have viral segments characteristic of two different families of swine flu, one typical of North America, where swine flu is endemic, and one typical of pig flu viruses from Europe and Asia. But we learned today that it also has viral segments seen in North American birds and in human seasonal influenza. Which of the segments is a bird segment and which is humans wasn't discussed in today's briefing, but the fact that the genetic sources comprise widely different geographies and species is highly unusual -- unusual at least as far as we know. We have little systematic information on swine viruses, so how common this really is we don't know for sure, nor do we know how recent. The virus is resistant to the older adamantane antivirals but sensitive to both oseltamivir (Tamilfu) and zanamivir (Relenza).

Whatever this is, it isn't seasonal influenza. The reported cases range from 9 years old to 54 years old, 3 females, 4 males. All have recovered and only one required hospitalization. The earliest case is from late March, the most recent just days ago. Symptoms are typical for influenza-like illness except that there seems to be a greater prominence of gastrointestinal symptoms (nausea, vomiting, diarrhea) along with the respiratory symptoms and fever. CDC emphasized they were in an active investigation mode and will keep sharing information as it develops. Clearly there is a lot more to learn about this.

Could this be the harbinger of an influenza pandemic? A pandemic is a global sized outbreak from a single strain of influenza...

Originally posted by redhatty
preliminary results show that this is antigen distinct, so no prior influenza exposure will give you protection

vaccine development is underway - talks of LIVE vaccine (dangerous - my personal comment) 1:26 PM
no rapid diagnostics for this is available 1:27 PM