Egyptian H5N1 exhibits differences; raises concerns
Disease profile indicates possible undetected cases.
Avian influenza H5N1 cases in Egypt differ from those recorded in Asia and Indonesia when compared to cumulative data for countries worldwide other than Egypt, Nigeria, and Turkey, as reported in PROmed.
As of April 2009, fatality rate from human H5N1 cases in Egypt was 34% (23 of 67), versus an average of 66% among WHO-confirmed cases from all countries other than Egypt (234 of 354) according to an analysis by J. P. Dudley, Science Applications International Corp., Modeling and Analysis Division, Rockville, Md., U.S.
Reported results indicated that a median age of 8 years for human H5N1 cases in Egypt between March 2006 and March 2009, versus a median age of 18 years for WHO-confirmed human cases globally between November 2003 and November 2006. Cases were reported most frequently among children younger than 10 years.
Females exhibit highest mortality
Females account for 90% of human mortality from H5N1 in Egypt, with confirmed mortality only reported among individuals older than 9 years. Although the sex ratio of cases in most countries is approximately 1:1, females outnumber males among confirmed cases in Egypt by a factor of nearly 2:1.
The average case fatality rate from H5N1 among children aged 0-9 years from all countries other than Egypt and Turkey is 59% with no confirmed fatalities among 33 children in this age group reported from Egypt.
The report said the existence of undetected fatal or non-fatal atypical or asymptomatic human H5N1 infections may be the cause of the existing anomalies with regard to age and sex in Egypt.
Clinically mild illness from highly pathogenic avian influenza H5N1 virus infection has been reported from children in most countries, but the early detection and treatment of possible cases may be a factor in the overall lower case fatality rate reported for the cases in Egypt.
Although there is no evidence of human-to-human transmission of the disease in Egypt, there is increasing concern that undetected H5N1 cases may be occurring based on evidence of family clusters.
H5N1 clusters involving highly probable human-to-human transmission have been documented in China, Thailand, Viet Nam, Indonesia, and Pakistan.