Sorry for the radio silence–I’ve been working on grants and manuscripts like a fiend, and so have tried to limit as many distractions as possible (which, unfortunately, includes blogging). However, the swine flu news is right up my alley, so I do just want to say a few words about it, and point you to some excellent stories already up elsewhere.
First, in case you’ve not been paying attention to the news in the last few days, there have been 8 reported cases of swine influenza infections in humans (6 in California and 2 in Texas, with additional suspected cases) and reports from Mexico suggesting as many as 1000 ill and 68 dead from influenza in the past month or so. Of the Mexican cases, a dozen thus far have been confirmed to be the same strain as the US swine flu strain from California/Texas.
What does all this mean? Much more after the jump.
It’s been awhile since I posted on anything flu-related here. Though cases of H5N1 continue to be uncovered on a regular basis, the media furor has died down a bit, and the government and local health agencies have been working behind the scenes to prepare for the possibility of an influenza pandemic. Long time readers will recall a post from awhile back, when influenza virologist Robert Webster gave a talk at the University. He emphasized:
…that, while H5N1 is the “bird flu” that’s receiving the lion’s share of media (and scientific!) attention right now, other serotypes of avian influenza have circulated recently, including H7N7 and H9N2. During the H7N7 outbreak in the Netherlands, 30 million chickens were destroyed, and there were over 300 human cases of conjunctivitis. There also was evidence of human to human spread, and one death from the outbreak. Additionally, there was serological evidence of H7N7 infection in pigs, which have long been a concern as a potential “mixing vessel” between avian and human-type influenza viruses. The take-home message: H5N1 ain’t all that has the potential to become a nasty pandemic strain, and we need to keep our eyes peeled.
Keep our eyes peeled indeed. This swine strain, serotype H1N1 (the “classic” swine flu serotype) is apparently a triple reassortant, carrying genes from human, swine, and avian influenza viruses. A few things make this outbreak concerning.
One, we see occasional swine influenza infections in humans on a somewhat regular basis. There was an outbreak associated with a fair in Ohio a few years back, and research by my colleague Greg Gray here at the university has showed that mild or asymptomatic infections of swine workers with swine influenza viruses are more common than we realize (David Brown of the Washington Post has a nice summary of that background here). However, those infected in California and Texas have no known contact with pigs–suggesting they acquired this virus from a human source.
Two, while the cases in the US have been mild and no deaths have occurred that we’re aware of, it seems in Mexico that young people are dying from this–a group that is typically not hard-hit by seasonal influenza viruses. Readers familiar with influenza and know the history of the 1918 influenza pandemic will recall that the “young and healthy” were disproportionally struck by that virus as well–so this knowledge is currently disconcerting and worrisome, but there are so many gaps in our information as far as what’s really going on in Mexico that it’s difficult to make heads or tails out of this data right now.
Third, is this really a new virus? So few influenza isolates are actually analyzed each year (in proportion to the number of people infected) that we aren’t sure yet whether this is something brand-new, or something that has been circulating at a low level for awhile, but just hadn’t been picked up. After all, H1N1 is a common serotype, so additional molecular testing is needed to determine that it’s “swine flu” versus “human” H1N1.
Fourth, and going along with that third point–how widespread is this? We have confirmed cases from Mexico, California, and Texas, which suggest it could be spreading in the southern parts of North America–but a breaking news report says that cases have also been confirmed in Kansas and New York, but it doesn’t say whether they’ve been definitively matched to the strains from the SW US and Mexico. The NY Times reports that some students at the NY school had recently traveled to Mexico and could have potentially brought the infection back from that trip, if it’s confirmed.
In summary, this is a fast-developing story, and it will take much more investigation and field work to determine the true extent of the virus’s spread in the population; to figure out where it originated (one blog suggests a Mexican hog confinement according to some local Mexican papers, but that is conjecture at this point); how it jumped to humans; and how efficiently it’s transmitted. Whether this burns out or spreads worldwide, it certainly shows once again the importance of surveillance and monitoring of influenza strains, and demonstrates that improving our infrastructure due to concerns about H5N1 will benefit us whether that serotype, or another emergent strain, ends up being the next global influenza threat.
Other sites to keep an eye on:
Daily Kos (Dem from CT)