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Commentary
Detailed
H1N1 Case Fatality Rates In India
Recombinomics
Commentary 12:40
July 31, 2010
A total of 157 out of 285 deaths since August last year in Pune had associated physiological illness or ailments like diabetes, hypertension and cardiac ailments. While 27 pregnant women succumbed to the virus from April till July this year, it is the age group of 16-45 that is mainly affected, according to health officials.
A total of 179 persons from this age group have died due to swine flu. There are 26 children below the age of five who have died due to the virus.
Dr Arun Jamkar, dean, Sassoon General Hospital, said they had conducted a survey of 28 patients who had died at the hospital and as many as 19 received delayed treatment and Tamiflu was started on day 4 or 5 of fever.
The above comments provide some detail on fatal H1N1 in and around Pune, India. The Ministry of Health recently released fatality rates on states throughout India which were alarming. Some states had rates in the 20-60% range, which rival rates for H5N1. However, pandemic H1N1 has replaced seasonal H1N1 worldwide, and in most countries it is the dominant strain of influenza, so the number of H1N1 infections far exceeds the number of lab confirmed cases, and most cases resolve without treatment.
However, even if the lab confirmed cases are limited to hospitalized cases, fatality rates of 20-60% are alarming and raise concerns that the frequency of D225G has increased. Media reports have described a “mutation” in H1N1 from several fatal cases, while additional reports suggests multiple “mutations” may have been detected.
Sequences from last year included changes in positions 156-159 which suggested immunological escape, with most changes at positions 158 and 159. These changes would reduce the effectiveness of immune responses to H1N1 infections or vaccines and may become more common in recent H1N1 infections. Immunological escape has also been reported for D225G, so recent H1N1 isolates may have increased levels of both of these changes.
Recent human H1N1 sequences from China have G158E and D225G as does swine H1N1. The spread of these markers could dramatically increase the case fatality rate.
D225G has been strongly associated with sever and fatal H1N1 in 2009 and 2010. It was also in 2 of the 5 HA sequences collected in 1918 and 1919 from fatal lung infections. Detection of D225G is dependent on the time and location of samples. It is most frequently found in bronchial lavage or direct sampling of lung samples.
Therefore, release of sequences such collections from recent cases
would be useful.
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