Dromedary camels and Middle East respiratory syndrome: MERS coronavirus in the 'ship of the desert']

Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel coronavirus, identified in patients with respiratory symptoms in the Middle East. Accumulating evidence points to dromedary camels as being reservoirs. MERS-CoV has been isolated from dromedaries, and dromedary MERS-CoV is nearly identical to human MERS-CoV. Camel and human MERS-CoV genome sequences from the same geographic areas cluster together. Both on the Arabian Peninsula and in Africa high percentages of adult dromedaries are seropositive for MERS-CoV. Young dromedaries (≤ 2 years) are more often acutely infected than adult camels. This means that the risk of human infection may be higher in camel breeding season (spring) when more naïve camels are present. Antibodies appeared to be present in dromedaries as early as 1992, while the first case in humans was recognised in 2012. Underdiagnosis, differences in risk profile, or subtle differences in the genetic make-up of MERS-CoV may explain the absence of MERS in humans before 2012, and in Africa.