A migrant worker has died of the H5N1 virus in southern China, the Hong Kong government said Tuesday, as the country confirmed its fourth outbreak of bird flu among poultry this year.

The woman who died Monday in Shanwei, a coastal city in eastern Guangdong province, tested positive for the deadly H5N1 avian flu virus, Hong Kong's Health Department said in a statement issued after receiving confirmation from China's Health Ministry.

Her death marked the country's 20th fatality from the deadly H5N1 virus and its third this year.

The woman had been in contact with dead poultry before becoming sick Feb. 16, a statement on the Web site of Guangdong's Health Department said Monday.

Meanwhile, China confirmed its fourth outbreak of bird flu among poultry this year but said it had been effectively contained.

Nearly 4,000 poultry were killed by the H5N1 virus in southwestern China's Guizhou province, the Agriculture Ministry said on its Web site Monday. Another 240,000 were culled to contain the outbreak.

China, which raises more poultry than any other country in the world, has vowed to aggressively fight H5N1, which has killed 232 people worldwide, according to the World Health Organization.

Bird flu remains hard for people to catch, but health experts worry the virus could mutate into a form that passes easily among humans, sparking a pandemic. So far, most human cases have been traced to contact with infected birds.

China has already reported two human deaths from H5N1 this year. Since 2003 when the virus began ravaging poultry stocks in Asia, the country has had 19 human deaths from bird flu, the WHO says.

Three outbreaks of bird flu in poultry were reported in China in 2008, two in the far western region of Tibet and another in the northwestern region of Xinjiang.