Hong Kong's Department of Health (DH) said Tuesday it is investigating into a case of anthrax in which a two-year-old boy developed symptoms of the disease on May 27 and died three days later.

Consultant in-charge of the DH's Disease Prevention and Control Division, Tse Lai-yin, said at a press conference the source of infection is under investigation.

Initial investigation revealed that the boy had a sudden onset of fever and anorexia on May 27. His condition deteriorated on May 30 with abdominal pain, irritability, vomiting and shortness of breath. He was immediately taken to a private hospital where he was certified dead shortly afterwards.

Based on the clinical features, postmortem examination and laboratory findings, the case is likely to have contracted the disease through the oral route.

"The family members of the boy are asymptomatic. However, they have been put under medical surveillance to ensure there is no infection," Tse noted.

She said anthrax is an acute infectious disease. It mainly occurs in animals like cattle and sheep but it can also infect human.

Tse stressed that transmission of the disease from person to person is very rare, and the incubation period ranges from one to seven days.

"Anthrax infection is very rare in Hong Kong. There have been three other cases reported in the past 20 years. Two of them in 1982 were occupationally acquired cutaneous anthrax and the remaining one in 1994 was a fatal sporadic case of intestinal anthrax involving a 13-year-old boy," she said. "There is effective antibiotic treatment for the disease. Early antibiotic treatment is essential because delay may lessen the chance of survival," she added.