Acting as a transportation system for the virus, the complex's plumbing system quickly became a key factor uncovered by Hong Kong investigators as they looked into reports of increased SARS cases.

U.S. plumbing fixtures - sinks, bathtubs, floor drains and toilets - are required to use a P-trap in its drainpipe, and the United states has not experienced a SARS outbreak on anywhere near the same level as China.

A recent initiative by plumbing and drain-cleaning franchiser Roto-Rooter makes consumers aware of the importance of keeping their plumbing and sewer systems clean. The company has created a list of consumer tips for preventing the spread of disease.

For further information and reports on SARS by the WHO, visit its Web site at www.who.int.