Hong Kong people are particularly prone to the flu because they talk too much and too loudly, according to a Chinese University professor. Professor Thomas Chan Yan-keung, of the department of medicine and therapeutics, said the flu virus took hold by lodging in the throat and airways, so keeping your mouth open for longer increased the risk of falling ill. People also did not realise that if they spoke too loudly for too long, their throats would become sore. 'The worst thing to do is to speak very loudly and too long,' the professor said. 'It is common in Hong Kong because there is too much background noise. You go to restaurants and people talk so loudly.' A hectic social life could also be a flu risk factor. 'Basically, you should get enough rest,' Professor Chan said. 'People would rather go out and have a drink or other entertainment after midnight. The next morning you get up at 6 o'clock. This is very unhealthy. Stop smoking too.' Professor Chan was speaking during the launch of a study into the economic impact of the flu. About 60 per cent of workers surveyed said they had suffered the flu or a similar illness last year, with 24 per cent of them becoming ill twice. One respondent said they had had the flu nine times.