A study published in the Lancet Infectious Diseases on 9 August 2013 by Reusken et al identified antibodies to MERS-CoV in camels both in Oman and Spain. A total of 50 out of 50 (100%) sera sampled from Omani camels and 15 of 105 (14%) of sera from camels from Spain had antibodies against MERS-CoV. Sera from European and Chilean sheep, goats, cattle and other camelids had no such antibodies. Generic viral nucleic acid tests used for the analysis of serum and fecal samples from Spanish dromedaries were negative. The authors concluded that MERS-CoV or a virus very similar to MERS-CoV has widely circulated among camels in Oman. (1) Of note, the European Centre for Disease Prevention and Control partially funded this study.
ECDC Comment 12-08-2013:
It is of utmost importance to identify the MERS-CoV reservoir and the transmission route to humans. For that reason, this study of Reusken et al. 2013 provides intriguing information, although it cannot be considered definitive proof that camels are a source of MERS-CoV.
Coronaviruses constitute a large family of viruses that may cause a range of illnesses in humans, as well as a number of diseases in a variety of animals. Previous studies have shown, for example, that coronaviruses can cause severe symptoms in newborn camels (Wuenschmann et al. 2002
, Tibary et al. 2006
). The high prevalence of antibodies to MERS-CoV in camels in Oman suggests widespread infection with MERS-CoV or a MERS-like virus. There are caveats to the findings of this study. The study does not exclude the possibility that there had been a cross-reaction with a related coronavirus to MERS-CoV (e.g. the laboratory methods identified antibodies to a similar virus as MERS-CoV but not exactly the same). Oman is located on the Arabian Peninsula, bordering with the Saudi Arabia, but no human cases of MERS-CoV have been reported there. The study does not include information on circulation or seroprevalence of MERS-CoV in animals from countries where human MERS-CoV has been found. Finally, since no viral particles were identified in the animals, it is not clear if they are a source of the disease or are incidentally infected.
In the epidemiological investigations carried out so far, direct animal contact of most of the MERS-CoV patients has been excluded as the probable route of infection. Few positive human cases have indicated contact with camels.
More studies are needed to confirm the reservoir or possible intermediate animal hosts. Results of this study do not explain how humans become infected with MERS-CoV.
ECDC staff who contributed to the public health development: Eeva Broberg, Elizabeth Bancroft, Cornelia Adlhoch, Pasi Penttinen, Rene Snacken, Andrew J Amato-Gauci