A spate of human deaths due to bird flu in China has sparked concern from the World Health Organization (WHO) and the U.S. Center for Disease Control and Prevention.

Millions of people have thronged to China to gather for Lunar New Year celebrations marking the Year of the Rooster.

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On Thursday, China's Hunan province reported its 17^th human case of bird flu this year.

According to Chinese state media, the patient had come into contact with infected chicken. Meanwhile, the people he came into contact with have reportedly not shown symptoms of bird flu.

The link to poultry is of particular interest as fowl dishes are popular during the lunar holiday dining in China.

On Thursday, the CDC issued a low-level travel advisory on China.

While not expressly warning against traveling to China, the U.S. health authority is advising people who travel to the country not to touch birds, or eat any undercooked food.

The spread of bird flu comes at an inopportune time for China and other Asian countries that are home to large populations celebrating the festival.

South Korea and Vietnam also experience mass travel, though not on China's scale.

The annual week-long holiday is described as the largest movement of people in a narrow window. The holiday will run from Friday to February 2 in China.

Approximately 40 countries, including some in Europe, have reported new outbreaks of bird flu.

"The rapidly expanding geographical distribution of these outbreaks and the number of virus strains currently circulating has put WHO on high alert," said WHO director-general Margaret Chan.

Chan made the comment while speaking at the start of the WHO's executive board in Geneva on Monday.

Bird flu typically infects poultry, but there are fears that the flu virus, which is prone to mutation, will change to one that can be distributed to humans.

Experts fear that Bird flu could potentially mutate to a fatal strain transmissible among humans, causing a pandemic.

Tagschina, bird flu, WHO