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Commentary
Jeddah MERS Camel and Case Sequence Update
Recombinomics Commentary
15:30
November 20, 2013
The above comments suggest that full MERS sequences from a Jeddah case (43M) and one of his camels will be completed next week. These sequences will almost certainly be virtually identical (well over 99%) due to positive results on the MERS PCR test. This test targets two regions of the MERS sequence which are designed to be specific for the sequences identified in human cases. All human sequences reported to date are >99.5% identical with the consensus sequences and for sequences from a common source such as the nosocomial transmission in Al Hasa, many sequences were greater than 99.99% identical to each other.
However, the virtual identity between the above case and camel will only indicate an interspecies transmission has occurred, which could be from camel to case, but also could be from case to camel. Media reports have noted that the above case had 8 camels in the barn adjacent to his residence (see map), but only one male camel was symptomatic. The asymptomatic camels may indicate MERS-CoV can be present in asymptomatic camels, or may mean that transmission among the camels may be limited.
Prior studies identified MERS-related antibodies, which were not detected in OC43 (beta2a) or SARS (beta2b) targets. However, the camel antibodies may have been directed against a beta2c CoV that was related to various beta2c isolates detected in bats. Only one bat beta2c sequence (from Bisha) was closely related to MERS. However, the MERS PCR data for the Jeddah camel suggests that the antibody results for camels on Oman and Egypt were due to prior MERS infection(s), but the antibodies may have been due to multiple exposures in the past and therefore may not predict active infections under circumstances reflected by the 8 camels described above.
In addition to the camel and case sequences cited above, more information on the detectability of MERS in various collections from different camel sites and times would be useful.
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