Clothes-lines outside bathrooms could have been used by rodents to enter flats
Rats could have been the main cause of the Sars outbreak at Amoy Gardens, which killed 42 residents and infected 329, according to a Hong Kong epidemiologist.
In an article published in The Lancet, Britain's authoritative medical journal, Stephen Ng Kam-cheung, special lecturer in epidemiology at Columbia University, said earlier hypotheses, including the so-called 'chimney effect', could not satisfactorily account for the distribution of cases and timing of the outbreak. Most cases happened on the upper floors and units 7 and 8 in the middle of the building.
'Roof rats prefer to forage for food above ground in elevated areas. They are also territorial and habitual, and tend to follow the same pathways between their nest and food sources and make return visits time after time,' he said, saying this explained the cluster of cases in units 7 and 8.
Clothes-lines installed outside the bathrooms of each unit provided convenient bridges for the rats as they travelled up and down the building, Dr Ng wrote.
'The infection could have passed from rats to man either by rats entering houses and leaving infectious material in bathrooms and kitchens, or by contamination of clothing on clothes-lines,' he said.
Although rats and cockroaches have previously been linked to the Amoy Gardens outbreak, other factors were regarded as the primary cause.