SINGAPORE -- A quarter of the buildings in Singapore are at risk of a potentially deadly outbreak of legionnaire's disease, DPA reported on Sunday. Three in four are safe, but Commissioner of Public Health Daniel Wang warned the remainder "are not quite up to the mark". New regulations covering air-conditioning cooling towers and water fountains drawn up by the Environment Ministry (ENV) will be enforced starting next month. Wang's remarks published in the ***Sunday Times*** coincided with data showing 30 cases of the illness were reported in the first 22 weeks of this year. Last year, there were 65. Three people died. The disease "has emerged as an important public health problem in Singapore because of our aging population and the high density of air-conditioned buildings," said the ministry in the Epidemiological news bulletin. Caused by a bacteria which thrives in warm, stagnant water and poorly-maintained man-made water systems such as air-conditioning cooling towers, whirlpool spas and decorative fountains, the disease afflicts the elderly and people with a preexisting medical condition weakening their lungs. The ENV carried out a survey of 190 cooling towers last year and found 113 tested positive for the Legionella bacteria. One of three outdoor water fountains were infected in addition to two out of six swabs taken from showerheads and taps in hotels and homes. Under the new rules, building owners or occupiers must clean and disinfect all cooling towers and fountains at least every six months and test for Legionella every three months. Those who fail to comply face a fine of 5,000 Singapore dollars (U.S.$2,700) for the first offence and subsequent fines up to double the amount.