The Middle East Respiratory Syndrome—How Worried Should We Be?

Perlman, Stanley

The genome of MERS-CoV was characterized within weeks of the isolation of the virus (4). Sequence analysis shows that it shares similarities with two previously identified betacoronaviruses, namely, BtCoV-HKU4, identified in Tylonycteris bats, and BtCov-HKU5, present in Pipistrellus bats, but its closest neighbor is a betacoronavirus isolated from Pipistrellus pipistrellus bats in the Netherlands. During the 2002-2003 epidemic, SARS-CoV adapted to human populations to such an extent that it could no longer infect bat cells. (An alternative explanation is that we have not yet identified the bat species that actually served as the ultimate source for SARS-CoV and that cells from this species would be sensitive to SARS-CoV.) In contrast, MERS-CoV infects both human and bat cells, suggesting a possible direct bat-to-human route of transmission (5) . However, since it is unlikely that most infected humans had direct contact with bats, it is more probable that another animal species common on the Arabian Peninsula, such as sheep, goats, cows, or even camels, serves as the direct source for infection. In support of the latter possibility, MERS-CoV neutralizing antibodies were detected in all dromedary camels sampled in Oman and even in a small percentage (14%) of camels in the Canary Islands (24) . Identification of animals that serve as intermediate hosts would help define human populations at risk and might also allow culling or quarantine of infected animals, a method that was used successfully in Hong Kong to decrease the load of pathogenic avian influenza A virus in domestic poultry populations (6) .