MERS Jeddah Camel and Case Match Concerns
November 12, 2013
Meanwhile, within the framework of MOH’s efforts to recognize and monitor the source of infection, it has tested some samples of the patient’s surroundings, including a group of camels in his own stockyard, whose initial laboratory tests proved positive for one of these camels.
The above comments from the Kingdom of Saudi Arabia Ministry of Health (KSA-MoH) website strongly suggest that the PCR positive on a sample from a camel belonging to a MERS confirmed case (43M) was based on the same assay used to detect MERS-CoV in humans. These probes are based on human MERS sequences and designed to be specific for the beta 2c coronavirus linked to human cases. Sequences from these cases are >99.5% identical to the consensus sequence, and higher for clade B sequences which are present in all human cases due to infections following the first confirmed case, 60M in July, 2012.
In contrast, beta 2c sequences from bats come from a research protocol which uses a universal probe designed to detect all coronavirus. Thus, most bat coronavirus sequences are not beta 2c, and for those that are, the identity with the human sequences is < 92.5%, with the exception of a sequence from an Egyptian Tomb bat in Bisha, which was 100% identical to one of the sequences (EMC/12) from the first confirmed case, who was from Bisha (but was treated and died in Jeddah). Thus, the other bat beta 2c sequences are decades or centuries away from the human sequences. However, be one bat sequence which matches the human case in Bisha is found in Egyptian tomb bats, which are localized to the area around Bisha and therefore would not be linked to the vast majority of human cases in KSA. Moreover, the bat sequence matches the clade A sequence which has not been detected in humans since July, 2012.