Updated at 6.58pm: Hong Kong people have to be vigilant about infectious diseases when travelling to Southeast Asia this summer, the Health Department warned on Thursday. The department said it had made the appeal in the wake of recent outbreaks of dengue fever in the region, as well as poliomyelitis cases and avian influenza cases in Indonesia. Statistics show more than 10,000 cases of dengue fever had been reported in Thailand and Indonesia in the first half of the year. Fifty-five people had died. Some 5,000 dengue fever cases have also been recorded in Singapore and the Philippines. About 70 people had died in these two countries. A senior health officer with the department, Henry Kong Wing-ming, on Thursday urged travellers to be vigilant about food, health and hygiene to avoid contracting infectious diseases. Dr Kong urged travellers to wear long-sleeved clothes and to use insect repellent on exposed parts of their bodies. He also advised that they use mosquito screens when rooms were not air-conditioned. 'Dengue fever is an endemic disease in Southeast Asian countries. The best way to prevent dengue fever while visiting these places is to avoid mosquito bites,' he explained. To guard against bird flu, Dr Kong said people should avoid direct contact with chickens and chicken faeces. They should also avoid visiting chicken farms. He said travellers should be cautious of symptoms of influenza-like illnesses - including fevers, sore throats and coughing. 'If symptoms develop, they should seek medical attention promptly and provide their travel history to the doctor,' added Dr Kong. For further details, visit http://www.travelhealth.gov.hk .