Five more people in mainland China have tested positive for H5N6 bird flu, leaving two dead and three others seriously ill, officials say.
It adds to a growing number of human cases which has led to urgent calls for increased surveillance.
The most recent case was announced on January 7, when health officials in Guangdong province said a 43-year-old woman had been hospitalized with H5N6 bird flu.
Chinese officials are providing only limited information about human cases of H5N6 bird flu and it often takes weeks before cases are publicly reported to WHO.
Most cases are first reported by the Hong Kong Health Department, which is closely monitoring human cases.
H5N6 bird flu is known to cause severe illness in humans of all ages and has killed nearly half of those infected, according to WHO.
The study highlighted several mutations in two recent cases of H5N6 bird flu. »