A World Health Organization report has found that 25 percent of the cases of 350 people in 14 countries who have contracted the H5N1 bird flu virus are unexplained. The report indicates this may be caused by small particles of virus-contaminated fluid that stick to surfaces or fertilizer made from infected bird feces that is somehow carried the virus into people’s noses or mouths.

As reported by the World Federation of Building Service Contractors.