Zhejiang Province – Credit Wikipedia
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Considering that H7 avian viruses have generally been viewed as `rare and mild in humans’, the reassortant H7N9 virus spreading in Eastern China continues to play against type, with the sixth fatality being reported this morning out of Zhejiang Province.
This report from the Chinese News agency Xinhua.
Sixth death from H7N9 bird flu reported
English.news.cn 2013-04-05 12:17:21
HANGZHOU, April 5 (Xinhua) -- East China's Zhejiang Province on Friday morning reported that a man has died from the H7N9 bird flu, bringing the death toll from the new deadly strain to six in the country.
The city has reported three infections to date, and two have died, the Health Bureau of Zhejiang Province said Friday.
According to the health bureau, the 64-year-old man surnamed Zhang, who is a peasant farmer of Huzhou City, died at hospital after rescue efforts failed on Thursday night and it was confirmed he was infected with the H7N9 strain.
So far, 55 people who had a close contact with Zhang have shown no abnormal symptoms.
China has confirmed 14 H7N9 cases -- six in Shanghai, four in Jiangsu, three in Zhejiang and one in Anhui, in the first known human infections of the lesser-known strain.
Shanghai authorities on Thursday reported four deaths, with Zhejiang now reporting two.
Six deaths are admittedly worrisome, but we currently lack sufficient data to gauge the CFR or Case Fatality Ratio, of this virus.
At this time we don’t have any idea how many total cases there are in China.
If there are a lot of mild cases out there not being treated in hospitals, then we are only seeing the the sickest of the sick, and the CFR would be lower than current numbers suggest.
If not . . . well, that would be a good news-bad news situation. It would suggest the virus isn’t transmitting among humans (good), but that it carries a high CFR (bad).
In truth, the number of cases (and fatalities) for nearly every disease go underreported. Health officials must then estimate the total disease burden based on mathematical models.
As the pyramid chart above indicates, only a tiny fraction of infectious disease cases are actually reported to health authorities. - Credit CDC
Fifteen years after it first emerged, the debate over the true CFR of the H5N1 avian flu virus is still hotly debated (see The Great CFR Divide).
And even when it comes to seasonal flu, the best we can do each year is to estimate the total number of cases and try to extrapolate a mortality rate.
As more data comes in, we should get a better `feel’ for the mortality rate of this virus , and if human-to-human transmission is established, eventually an estimate of the basic reproductive number (R0) of this virus.
R0 (pronounced R-naught) is the the number of new cases in a susceptible population likely to arise from a single infection.
With an R0 below 1.0, a virus (as an epidemic) begins to sputter and dies out.
Above 1.0, and an epidemic can have `legs’.
But those numbers will – of necessity – be estimates, and often vary over time, and by geographic location.
For now, our understanding of the threat posed by this H7 virus remains limited. It could easily fade back into the woodwork, or it could become a contender.
The next few days should provide better clues as to where all of this is going.
Stay tuned.
