Identification of risk factors associated with highly pathogenic avian influenza H5N1 virus infection in poultry farms, in Nigeria during the epidemic of 2006–2007

We conducted a matched case–control study to evaluate risk factors for infection with highly pathogenic avian influenza (HPAI) H5N1 virus in poultry farms during the epidemic of 2006–2007 in Nigeria. Epidemiologic data were collected through the use of a questionnaire from 32 case farms and 83 control farms. The frequency of investigated exposure factors was compared between case and control farms by using conditional logistic regression analysis. In the multivariable analysis, the variables for (i) receiving visitors on farm premises (odds ratio [OR] = 8.32; 95% confidence interval [CI] = 1.87, 36.97; P < 0.01), (ii) purchased live poultry/products (OR = 11.91; 95% CI = 3.11–45.59; P < 0.01), and (iii) farm workers live outside the premises (OR = 8.98; 95% CI = 1.97, 40.77; P < 0.01) were identified as risk factors for HPAI in poultry farms. Improving farm hygiene and biosecurity should help reduce the risk for influenza (H5N1) infection in poultry farms in Nigeria.