In the Hong Kong study, which focused on the 2003 SARS outbreak at the Prince of Wales Hospital, 41 percent of patients admitted to the ward in which the first SARS patient was staying became infected. Proximity to the bed of the first case seemed to be strongly linked with incidence of infection-two-thirds of patients in the same bay and half of patients in an adjacent bay were infected with SARS, while only 18 percent of patients in distant bays were infected.
The Hong Kong researchers, led by Ignatius T.S. Yu, MBBS, MPH, of the Chinese University of Hong Kong, speculate that the increased risk of infection with closer proximity to the index SARS case suggests airborne transmission. Although they do not have "direct proof" of airborne transmission, according to Dr. Yu, "no other known routes of infectious diseases transmission could adequately explain the spread of the disease in the outbreak, and hence we feel that the evidence is quite strong."
An editorial accompanying the Toronto study, by Tommy Tong, MBBS, of Princess Margaret Hospital in Hong Kong, emphasized the scientific significance of discovering SARS coronavirus in the air in a patient's room. "Although the possibility of airborne dissemination of SARS coronavirus has been controversial," said Dr. Tong, "this important work shows beyond doubt that SARS coronavirus aerosol generation can occur from a patient with SARS." The Hong Kong study provides additional, complementary evidence that the virus may be capable of spreading through the air.