HONG KONG • Taiwan and the southern Chinese island province of Hainan are at greater risk than anywhere in mainland China of having locally transmitted cases of the Zika virus, according to a prominent virologist.

Taiwan and Hainan both have populations of the Aedes aegypti mosquito, believed to be the main carrier of Zika. The virus has infected 1.5 million people in Brazil alone in recent months, while also spreading throughout most of South America, Central America and the Caribbean and into Mexico, said Dr Peter Piot, director of London School of Hygiene and Tropical Medicine and co-discoverer of the Ebola virus.

The rest of southern China, including Hong Kong, has a different kind of mosquito, Aedes albopictus. It may also be able to carry Zika but is probably less efficient at transmitting it to people, Dr Piot said in Hong Kong on Tuesday.

The northern two-thirds of China, including big cities like Shanghai and Chongqing, lie farther north than the usual range of either mosquito, according to a map that Dr Piot presented as part of a videotaped speech at the Foreign Correspondents' Club. But the disease might also spread through sexual transmission farther north, he warned.

Mosquito season has barely begun in China this year, limiting the risk so far.

The National Health and Family Planning Commission in Beijing has disclosed 12 cases of people carrying the Zika virus so far, all of whom were said to have acquired the disease while travelling outside China.

According to the Hong Kong Department of Health, there have been no cases of Zika in the territory. Dr Malik Peiris, a virologist at the University of Hong Kong, said Hong Kong could easily end up with a case from someone returning from an area with infections.

NEW YORK TIMES