Answer (a) — incorrect: While it is correct that the causing agent of the SARS epidemic is coronavirus and the most likely mode of spread of infection is person-to-person, this answer does not provide information on the control measures which will stop the outbreak.

Answer (b) — correct: Based on what we know about SARS so far, the best formulated hypothesis is one that includes coronavirus as the most likely agent of infection, spread of SARS via person-to-person and isolation of cases and quarantine of exposed as measures of control of the spread of epidemic.

Answer (c) — incorrect: From the previous SARS epidemic we have no data regarding its mode of transmission via mosquitoes. While it is certainly true that airplane travel has played a role in the spread of the SARS epidemic around the globe, it is unlikely that banning air travel to affected areas will completely stop the epidemic as the epidemic can spread by many other ways, e.g. local travel by buses and on foot.

Answer (d) — incorrect: Symptoms which are characteristic of West Nile virus infection differ from those of SARS infection, and therefore, the case definition of SARS cannot be met. In addition, the CDC has established that SARS is caused by a virus from the corona family, not by a West Nile virus. It has also been established that the most likely way to spread SARS is person-to-person