221315 Evaluating the seasonality of human influenza A/H5N1 in Egypt and the effects of weather conditions

Wednesday, November 10, 2010 : 9:05 AM - 9:20 AM

Eleanor Murray, MPH , Disability Prevention, Occupational Health and Safety Agency for Healthcare (OHSAH) in BC, Vancouver, BC, Canada
Stephen S. Morse, PhD , Department of Epidemiology, Columbia University, New York, NY
The seasonality of human influenza in tropical regions is not well understood. Although H5N1 has caused over 250 human deaths worldwide, and several studies have evaluated environmental risk factors for H5N1 in poultry, there has been no systematic study of climate or seasonality of influenza A/H5N1 in either humans or poultry. In order to better understand influenza seasonality, a secondary data analysis was conducted on human influenza A/H5N1 cases in Egypt (n=50), using cases reported to the World Health Organization through May 1, 2008. In addition, the distribution of human cases was compared to reported poultry outbreaks in these countries. Usual regression methods were determined to be inappropriate since the pattern of seasonality of H5N1 was unknown and the H5N1-climate dataset violated key assumptions of these methods. Instead, Fourier analysis was used to determine the pattern of seasonality of cases and to assess the contributions of weather variables. This method allowed direct evaluation of seasonality or periodicity, by determining the frequency that best fit the data. Human H5N1 cases occurred with a period of 1.18 years/cycle, and were linearly related to climate (κ2≥0.94). Incidence peaked when precipitation was high; temperature and absolute humidity, low; and relative humidity, intermediate conditions outside the range typically described as optimal for influenza transmission and survival. Finally, occurrence of large poultry outbreaks was not a good predictor of human cases. The results will inform models of influenza spread in tropical areas and allow better targeting of preventive interventions for human H5N1.

Learning Areas:
Environmental health sciences
Epidemiology
Protection of the public in relation to communicable diseases including prevention or control

Learning Objectives:
Describe the seasonality of human influenza A/H5N1 and the association of human cases with meteorological variables

Keywords: Emerging Diseases, Environmental Health

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I designed and conducted the analyses for this project.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

Back to: 5041.0: Epidemiology of influenza