China is big and has lots of people.

Up to 96 cases now. Case fatality rate is currently 66% (18 dead, 9 discharged from hospital).

So far, H7N9 seems to be hitting the elderly the hardest, which is more like seasonal flu and unlike certain pandemic strains in the past, which strike down the young. However, that could totally change, depending on the kinds of mutations that it may undergo in the days ahead.

I'll be out of the country and out of touch for a week starting tomorrow, so no more updates from me for a while. So, breathe easy while I'm gone!

Well, I'm back. Kind of nice to not really see any news for a whole week.

Not many dramatic developments over the H7N9 flu while I was gone, but no encouraging news. We're up to 126 cases since a week ago, and their locations are spreading outward and southward. Taiwan reported its first case, a Taiwanese businessman who frequently traveled to mainland China. More ominously, three healthcare workers tending to H7N9 patients and wearing full protective gear have also fallen ill.

This week includes the May Day holiday in China, so I would not be surprised to see a spike in cases about a week from now as people return from holiday travels to or through affected areas.

The Chinese government has officially announced that genetic testing has shown that poultry from live markets are the source of the infection. But as I reported before, this flu virus does not seem to really sicken chickens, which makes it much more difficult to monitor chicken flocks for disease, and likely increases the incentive for poultry farmers to try and hide sick birds and avoid having their whole flocks culled as a preventative measure.

Seems the pace of new infections has leveled off, likely due to regional closure of live poultry markets, thus minimizing the contact between live chickens and humans. However, there is still much that is unknown about where the virus is coming from and how it is being transmitted.

Massive closure of poultry markets is not really a long term solution and is costing billions in lost business. More like the Chinese have bought themselves some time. Since the virus is mild in chickens, unlike another bird flu, H5N1, I doubt H7N9 will burn itself out anytime in the near future without massive cullings of flocks or an effective bird vaccine is created.

It's interesting that I haven't seen the case fatality rate statistic used anymore. Instead, I see a generic "mortality" used instead, and quote about 20-25% because about 1 out of 4 or 5 confirmed cases have died. The thing is, many of those patients are still in the midst of being sick so we don't know which way they will go yet.

There's an equal number of patients who have died as have recovered, so the case fatality rate is 50%, not 20%, and is a more appropriate measure of the lethality of H7N9 during the midst of an epidemic than the "mortality" statistic being bounced around the news.

Remember, in comparison, the Spanish Flu had a case fatality rate (or since it's over and done with, a mortality rate) of 2-3%.

More good news on the H7N9 front. Shanghai, ground zero for H7N9 cases, has recently announced that emergency surveillance measures will be ended. Activities involving live poultry are still banned in the city, though (including raising or selling them).

New cases have crept up very slowly only to 131, which is good, but the location of new cases continues to spread from southeast China, which is worrisome since the route is transmission is still unknown.

The case fatality rate is now 38%, with 35 deaths. The Chinese released the results of tests on 20,000 people with possible flu-like symptoms, and they found only a handful of infected with H7N9 among them, indicating that mild cases of H7N9 seem to be rare. Basically, if you catch it, chances are, you get very, very sick.

The lone case outside China, a Taiwanese businessman, has been transferred out of the ICU. That's a good sign because he was previously on a ventilator and also undergoing ECMO--the desperate last-ditch measure that became widespread during the H1N1 "swine flu" pandemic. The healthcare workers who tended to him and became ill turned out not to have H7N9.

More Chinese provinces are ending their H7N9 emergency measures. Zhejiang, Jiangsu and Shandong are the three new ones. So, the immediate threat of H7N9 is rapidly receding.

There was an interesting report about Taiwan's lone H7N9 case. His body carried both a drug-sensitive and drug-resistant strain of the virus at the same time, which made his treatment tricky. The theory is that he caught the drug-sensitive strain but that it acquired the drug-resistant mutation while he was infected.

H7N9 increasing again; stay tuned:

Washington Post article on H7N9

Included in the comments is a link to this downloadable book that is very detailed:
Bird flu book

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