The World Health Organization announced Tuesday that laboratory tests have confirmed an additional case of H5N1 infection in Vietnam.

The patient is a 15-year-old boy from Thanh Hoa Province, who was admitted to hospital on Feb. 9. He remains under treatment in Thanh Hoa Hospital.

To date, human cases have been reported in Vietnam and Thailand. Vietnam has reported 21 laboratory confirmed cases, 14 of which were fatal, while Thailand has reported eight laboratory confirmed cases, six of which were fatal.