At the time of this posting, the official WHO count remains at 33 cases and 9 deaths, but Chinese media reports 38 H7N9 cases and 10 deaths. The newest cases are from Shanghai (three cases and one death) and Jiangsu (two cases). HealthMap, along with several other disease surveillance groups, bloggers, scientists, and officials, has been closely following the outbreak as it unfolds.
The cases are geographically clustered in eastern China: Shanghai (18 cases and 6 deaths), Jiangsu Province (12 cases, 1 death), Anhui Province (2 cases, 1 death) and Zhejiang Province (6 cases and 2 deaths). The five cases reported this morning are from Shanghai, Jiangsu and Zhejiang Provinces.
Chinese media reports that genetic reassortment between wild birds from “east Asia” and chickens from “east China” are the source of the virus. The finding from scientists in Shenzen eliminates pigs as a potential host (if you’re just joining us, check out our previous H7N9 post to learn more about reassortment. You may also want to visit this fantastic infographic on influenza in different species from David McCandless).
Chinese Influenza Epidemic with Search Query from Baidu. Image by Qingyu Yuan, HealthMap 2013.
If this is true, the geographic spread makes some sense, at least according to Declan Butler. In a recently published piece in Nature, Butler explains that birds at live poultry markets in China arrive from a variety of sources and each source may send its birds to different markets. Butler also states that officials have found evidence of H7N9 in pigeons, ducks and chicken at live poultry markets in Shanghai and Hangzhou. As a result, live poultry markets in Shanghai, Nanjing and Hangzhou have been shut down and thousands of birds have been culled.
Among the most concerning characteristics of this virus are that it is a completely new virus in humans, so we do not have any immunity against it, and that it has adapted to infect mammal cells. So how can we protect ourselves against it?
The New York Times recently reported that the CDC was participating in the production of a seed vaccine (meaning a vaccine made from a laboratory-produced virus) to protect against H7N9. In a press briefing on April 5, CDC Director Dr. Tom Frieden explained that vaccine manufacturing was out of “an abundance of caution,” and that it would only be produced if there is evidence of human-to-human transmission.
As Declan Butler writes, this is indeed the question that is on everyone’s minds: will the “novel avian influenza virus […] rapidly fizzle out, become established in animal hosts to fuel future human outbreaks, or morph into a virus that can spread easily between people and spark a deadly pandemic.”
For the time being, there is no evidence of human-to-human transmission. The WHO is sending out 140 character reassurances via Twitter. In fact, last week, the WHO announced that it would be publishing updates on Twitter first, and in press releases after. That the WHO is tweeting these statements is significant; it suggests an acknowledgement of the important of social media in disease detection and response.
There is some good news to be gleaned from using online data sources for disease surveillance. A HealthMap research fellow has been studying flu-related searches on Chinese search engine Baidu in relation to influenza cases. He has found a meaningful correlation between seasonal influenza and influenza-related searches on Baidu based on the past four years of data. Using these methods on recent data, he found a spike in searches this April, after the breaking news on the first H7N9 cases. The absence of an increase in flu-related searches before the H7N9 news broke indicates that there has not been an undetected surge in cases prior to the official announcement. While deducing true disease incidence from measurement of human behavior is an imperfect science, research in the past has demonstrated utility in this approach (Google Flu Trends, for example). As epidemiologists cautiously watch this outbreak develop, we welcome this bit of good news.
As an aside, if you’re somewhat new to H7N9 monitoring, Twitter provides a wealth of information. Consider following Crawford Kilian (@Crof), who is keeping a chronology of the confirmed cases and deaths, as well as posting pertinent and timely contextual information on the outbreak; Canadian reporter Helen Branswell (@helenbranswell), who has been providing excellent analysis for the Canadian media outlets; Mappy Health (@mappyhealth), who has been tracking tweets related to H7N9 and has created a nice visual of the outbreak as tweeted; George Chen (@george_chen), reporter for South China Morning Post; Maryn McKenna at Wired (@marynmck), Declan Butler at Nature (@DeclanButlerNat), and Michael Coston (@Fla_Medic) of Avian Flu Diary. This is by no means an exhaustive list. Simply search for “#H7N9” on Twitter and you’ll find a lot of information on the outbreak and who is tweeting what and when. Be cautious, however, of some of the challenges we face in digital disease detection: fear mongering, misinformation, and still circulating dated reports.