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In an exclusive interview with Reuters News today, CDC Director Thomas Frieden stated that the H7N9 virus – which has recently infected more than 130 people in China – does not have the ability to transmit from human-to-human, and it its current form cannot spark a pandemic.
He warns, however, that the virus could mutate at any time, and potentially pose a pandemic threat.
This from Reuters.
REUTERS SUMMIT-Current China bird flu strain can't cause pandemic -CDC
Source: Reuters - Mon, 6 May 2013 03:55 PM* Virus could mutate -CDC director
* If virus mutates, could cause "severe pandemic"
* H7N9 began infecting people in February
By Julie Steenhuysen
NEW YORK, May 6 (Reuters) - The head of the U.S. Centers for Disease Control and Prevention says the current strain of bird flu that is causing illness and deaths in China cannot spark a pandemic in its current form - but he added that there is no guarantee it will not mutate and cause a serious pandemic.
In an exclusive interview at the Reuters Health Summit in New York, Dr. Thomas Frieden, director of the CDC, said more than 2,000 people have been in contact with infected individuals, and only a handful have become ill.
The fact that we’ve not seen an exponential rise in H7N9 cases in China supports the idea that this virus – if it is being transmitted other than by direct contact with poultry – is doing so very ineffectively.
The yardstick by which human transmission is measured is called the R0 (pronounced R-naught) or Basic Reproductive Number. Essentially, 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’.
Assuming there are not a lot of undiagnosed mild or sub-clinical cases out there (something we can’t know with absolute certainty until seroprevalence studies are done), then the recent leveling off of cases would certainly suggest H7N9’s R0 as being well below 1.0.
That said, the hallmark of influenza viruses is that they are constantly changing.
Which is why what can be said to be true about H7N9’s abilities today, can not be guaranteed to hold true next week, or next month, or next year.
