World Health Organization (WHO) senior communicable diseases specialist David Heymann warns that it will be difficult to detect a recurrence of severe acute respiratory syndrome (SARS) next winter because those who are infected with it first carry a very low level of the virus, which delays diagnosis. Medical authorities may have to isolate and treat those with similar viruses that appear during colder weather, since there is currently no diagnostic test for SARS that can reveal its presence early in the infection. Medical researchers think that there will probably be another SARS outbreak this winter. The WHO has listed nearly 8,500 SARS cases around the world since its first detection in China last November, and over 90 percent of those cases were in mainland China, Taiwan, and Hong Kong.