by Laidback Al
Recent information published about the number of infections and testing among suspected H5N1 human cases in Egypt provides a basis for estimating the current attack rate (AR) and case fatality rate (CFR) of H5N1 in Egypt.
1. Since the first case of human infection of H5N1 in Egypt in March of 2006, a total of 2365 individuals had flu/influenza-like symptoms and were suspected of being infected with H5N1.
2. All of these 2365 individuals received oseltamivir (Tamiflu).
3. Only about 33% (about 780 individuals) were actually tested for H5N1.
4. About 66% (about 1585 individuals) were NOT tested for H5N1, but experienced flu/influenza-like symptoms and were treated with oseltamivir (Tamiflu).
5. Of the approximately 780 individuals tested, 22 tested positive and were confirmed for H5N1. These data imply a attack rate (AR) of 2.8% among all 780 tested individuals. Thirteen of the 22 confirmed individuals died, a case fatality rate (CFR) of 59%.
A. Assume that the Tamiflu was effective in treating all H5N1 infected individuals among the group of 1585 that were not tested.
B. Assume a similar AR of 2.8% for the other 1585 individuals that were not tested but given Tamiflu.
Then it would follow that as many as 44 individuals in the non-tested group of 1585 individuals could have been infected with H5N1, but recovered after receiving Tamiflu.
Adding 44 potentially recovered cases to the 13 dead and 9 recovered confirmed cases would give a CFR of about 20%.
These data suggest, based on a generous interpretations of the number of infected, but recovered, unconfirmed human cases in Egypt, that the minimum CFR could be about 20%. If, in fact, none of the 1585 non-tested individuals were infected with H5N1, then the CFR in Egypt is 59% based on all 22 confirmed cases. Assuming a new strain of H5N1 is infecting humans this flu season, then the CFR could be as high as 87.5% (7 deaths among 8 individuals, since October 2006).
The CFR in Egypt at this time could range between a high of 87.5% to a low of about 20% based on the speculative discussions here. For the CFR to be any lower, there would have to be very many infected, but asymptomatic, human cases of H5N1 in Egypt.
Thanks to lili61 for posting the article and for Anne for providing the initial translation, and to NS1 for additional comments.