Via her blog Superbug, Maryn McKenna writes an important post: H7N9 Flu, Year Two: What Is Going On? Excerpt:
Cast your mind back to about this time a year ago. A novel strain of flu, influenza A (H7N9), had emerged in China, in the provinces around Shanghai. International health authorities were deeply concerned, because any new strain of flu bears careful watching — and also because, on the 10th anniversary of the SARS epidemic, no one knew how candid China would be about its cases.
By the time peak season for flu ended in China, there had been 132 cases and 37 deaths from that newest flu strain. But, confounding expectations, the Chinese government was notably open about the new disease’s occurrence, and scientists worldwide were able to ramp up to study it. Still, no one could say whether that flu would be the one to make the always-feared leap to a pandemic strain that might sweep the globe. As with other, earlier, worrisome strains of flu, science could only wait and see whether it might return.
And now it has.
In the wake of Lunar New Year, and the enormous internal migration it triggers as people return home for celebrations, China has been reporting a steady flow of new cases of H7N9: seven one day, 10 on another, 14 on the day after that. This morning, the World Health Organization announced that the Chinese government notified it over the weekend of 15 new cases, including one death. Simultaneously, Xinhua News reported a case of H7N9 entering mainland China: a 6-year-old boy who crossed from Hong Kong.
The current case count is very hard to pin down. (In a story 10 days ago, expert flu reporter Helen Branswell presciently remarked: “The numbers are rising so fast it’s tough to keep track of where the count stands. Between the time this article is written and when it is read, the numbers will almost certainly change.”)
The WHO does not add cases to its tally until they have been lab-confirmed and acknowledged by China’s Ministry of Health, so the totals it reports, while thoroughly vetted, lag behind actual cases by days or weeks. The most rapid, but not lab-confirmed, count is compiled by the community of flu geeks collectively known as FluTrackers, and is crowdsourced from translations of Chinese-language media. Their current tally stands at 336 cases since H7N9 first surfaced.
That total is an important number, for two reasons. First, because the number of cases in the “second wave” of H7N9 (from late autumn 2013 until now) exceeds those in the first wave of outbreaks. And second, because it suggests that H7N9 is managing more rapid spread than the flu strain that has been the subject of the greatest international concern, avian flu H5N1: 336 in 12 months, versus 650 in 10 years.