China: Baffling Resistance to SARS

A small but intriguing clue has emerged from the SARS fight in China. A select population in Guangzhou, the southern Chinese city where the epidemic apparently began in November, appears to have resisted infection.

At the peak of the outbreak in January and February, patients with the then-mystery illness were placed on the same floor of People's Hospital No. 8 as AIDS patients. Guangzhou authorities placed SARS patients on one side of the elevator bank and AIDS patients on the other side. Health care workers traveled throughout the two sides of the floor, and some of the doctors and nurses contracted SARS.

However, none of the several dozen AIDS patients there -- or their visitors, some of whom were HIV-positive -- developed the disease. "I am wondering why there was no SARS virus coinfection in the AIDS cases," said Dr. Zhang Fujie, director of AIDS treatment and care for China. Dr. Cheng Feng of the China/UK HIV/AIDS Project proposed that perhaps drugs given to AIDS patients to control HIV could be blocking SARS infection. Drs. Yuen Kowk-yung and David Ho, of the University of Hong Kong and the Aaron Diamond AIDS Research Center, respectively, are exploring the AIDS apothecary for an effective SARS treatment.

Even more puzzling is that the most effective HIV drugs, protease inhibitors, are not available in Guangzhou. Few Chinese have access to any but the cheapest, least effective HIV drugs, according to an HIV outpatient and activist who asked only to be identified as Thomas.

SARS continues to present scientists with numerous perplexing aspects. Some speculate that rather than SARS killing human cells, the immune system's overreaction to it actually precipitates lung cell destruction, contributing to the disease's hallmark of acute pneumonia. It is theorized that death may result from an aberrant or overly sensitive immune system. Should this theory be proved correct, it is possible that HIV patients are at a lower risk for SARS precisely because they lack strong immune responses. Also supporting this theory: The most effective SARS treatment so far is steroids -- agents that stifle the immune response.

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