Update H7N9 AI outbreak in China, ECDC, April 11, 2013

China is opening up and learnt from the past it seams. They started to share information, but only in relation to the human cases. Not a word about the source of the outbreaks. Not a word over where the infected farms are. Pigeons are very unlikely to spread the virus through markets. If you have to run the biggest town of China, providing the people with eggs and poultry meat, you need extremely large farms, close to the customers. Well-protected, because of the risks that the animals are going to be infected. Think what the financial consequences would be if these farms should have to e closed.

One of the things that is important when it comes to human infections is the Case Fatality Ratio CFR of the virus, commonly called a case fatality rate, although it isn’t technically a rate but a proportion. On 10 April 2013, 33 human cases of infection with influenza A(H7N9) virus have been reported in four provinces of China: Shanghai (15), Jiangsu (10), Zhejiang (6) and Anhui (2). since 31 March 2013, with onset of disease between 19 February and 3 April 2013. The date of disease onset is currently unknown for five patients. Nine patients died.

That means that the current CFR = 27%, but there are still 21 are severe cases and three are mild cases. The median age is 64 years with a range between 4 and 87 years; 11 of them are females.

To calculate CFR, you can only count resolved cases, that is, people who have recovered or died. We don’t know for sure how many are still in hospital, but it appears to be a large number, many in critcal condition. Even if some of these survive, they obviously would not have without advanced care. This will not be available in a severe pandemic.

The true CFR of this virus could become as high as 90%. To decrease the CFR significantly, we would have to assume thousands of unreported mild cases. If this is true, we will see cases in other countries very soon.

We are either looking at a virus which is already pandemic-ready or at a virus with a 90% kill rate which is 2 mutations away from pandemic status. I would actually prefer the former as the latter is a potential species-wiper.

Update H7N9 AI outbreak in China, ECDC, April 11, 2013 from Charm Key