A vaccination programme may be provided for residents in specific districts if there is a sudden rise in cases of Japanese encephalitis, a senior health official said yesterday. Thomas Tsang Ho-fai, consultant for communicable diseases at the Centre for Health Protection, said: 'We would not rule out the possibility of having a vaccination programme for residents of particular areas if we observe a sudden rise in the number of Japanese encephalitis cases in the same district or residential complex, say about 10 cases.' However speaking on a Commercial Radio programme, Dr Tsang said that the government did not at the moment see the need for a vaccination programme. He also warned that Japanese encephalitis was common on the mainland, Thailand and a number of other countries in Southeast Asia. Dr Tsang said anyone who planned to travel to affected regions for a long period of time or was staying in 'high-risk' areas might consider having the vaccine. The consultant also warned that the next few weeks would be crucial in the control of Japanese encephalitis because the rainy season was approaching, which might increase the population of disease-spreading mosquitoes. Meanwhile, the 45-year-old man confirmed with Japanese encephalitis remained in a critical condition yesterday. The man developed a fever, headache and drowsiness on June 8 and sought treatment later that day. Earlier this month, a 29-year-old Indonesian domestic helper, who worked in Kwai Chung, died from Japanese encephalitis. Dr Tsang said it was not usual to have two cases in a month. But he said it was too early to assess the risk of an outbreak until a blood test to identify people with antibodies to the virus had been carried out. According to the World Health Organisation, Japanese encephalitis is the most significant form of viral encephalitis in Asia, accounting for at least 50,000 cases of clinical disease and 10,000 deaths each year, mostly among children.