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In late summer through early winter of 1998, there were several outbreaks of respiratory disease in the swine herds of North Carolina, Texas, Minnesota, and Iowa. Four viral isolates from outbreaks in different states were analyzed genetically. Genotyping and phylogenetic analyses demonstrated that the four swine viruses had emerged through two different pathways. The North Carolina isolate is the product of genetic reassortment between H3N2 human and classic swine H1N1 influenza viruses, while the others arose from reassortment of human H3N2, classic swine H1N1, and avian viral genes. The hemagglutinin genes of the four isolates were all derived from the human H3N2 virus circulating in 1995. It remains to be determined if either of these recently emerged viruses will become established in the pigs in North America and whether they will become an economic burden.
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...
Preliminary tests in Mexico were said to show that cases had influenza A/H1N1, influenza B or parainfluenza. The first two are the this years' main seasonal influenza viruses. Parainfluenza is another common cause of respiratory disease. One of the major questions is whether the H1N1 is human seasonal influenza, like the H1N1 swine flu variant just reported by CDC, or something else. Since three different viruses are mentioned, we also need to know which one is the predominant virus in the current outbreak. Several news outlets report that 51 Mexican clinical specimens have been sent to the Canadian Public Health Agency laboratory for genetic characterization.
Originally posted by spinkyboo
updated every 10 miinutes
The unique strain of swine flu found in seven people in California and Texas has been connected to the deadly flu that has broken out in Mexico, killing as many as 60 people, NBC News has confirmed.
The strain has never been seen before and is raising fears of a possible pandemic.
The World Health Organization said it was concerned at what it called hundreds of "influenza-like" cases in Mexico, and also about the confirmed outbreak of the new strain of swine flu in the United States.
Mexico canceled classes for millions of children in its sprawling capital city and surrounding area on Friday after authorities noticed a higher number of flu-like deaths than normal in recent weeks.
"It is a virus that mutated from pigs and then at some point was transmitted to humans," Health Minister Jose Angel Cordova told the Televisa network.
The World Health Organization said on Friday that it was convening an emergency committee to advise whether outbreaks of swine flu in the United States and Mexico constituted an international public health threat.
The White House is closely following the outbreak of a new strain of swine flu in the United States and President Barack Obama has been informed, an administration official said on Friday
Originally posted by infinite
Mexico is nearing a 1,000 reported cases so far. The poverty and deprivation will bread the virus more - a rapid contagion is highly possible. We could be talking millions by next week.
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