Human-Dromedary Camel Interactions and the Risk of Acquiring Zoonotic Middle East Respiratory Syndrome Coronavirus Infection

Abstract

Middle East respiratory syndrome coronavirus (MERS-CoV) cases without documented contact with another human MERS-CoV case make up 61% (517/853) of all reported cases. These primary cases are of particular interest for understanding the source(s) and route(s) of transmission and for designing long-term disease control measures. Dromedary camels are the only animal species for which there is convincing evidence that it is a host species for MERS-CoV and hence a potential source of human infections. However, only a small proportion of the primary cases have reported contact with camels. Other possible sources and vehicles of infection include food-borne transmission through consumption of unpasteurized camel milk and raw meat, medicinal use of camel urine and zoonotic transmission from other species. There are critical knowledge gaps around this new disease which can only be closed through traditional field epidemiological investigations and studies designed to test hypothesis regarding sources of infection and risk factors for disease. Since the 1960s, there has been a radical change in dromedary camel farming practices in the Arabian Peninsula with an intensification of the production and a concentration of the production around cities. It is possible that the recent intensification of camel herding in the Arabian Peninsula has increased the virus' reproductive number and attack rate in camel herds while the 'urbanization' of camel herding increased the frequency of zoonotic 'spillover' infections from camels to humans. It is reasonable to assume, although difficult to measure, that the sensitivity of public health surveillance to detect previously unknown diseases is lower in East Africa than in Saudi Arabia and that sporadic human cases may have gone undetected there.

Keywords: Arabian Peninsula; MERS-CoV; camels; coronavirus; zoonoses.

Figure 1

Age and sex distribution among primary and secondary cases 2 March 2012–23 July 2014 (primary cases n = 355*, secondary cases n = 310**). *162 cases were excluded due missing age or sex data. **26 cases were excluded due to missing age or sex data.ECDC line listing: data compiled from WHO and Ministries of Health websites around the world.

Figure 2

Distribution of confirmed cases of MERS‐CoV by of onset and transmission pattern, 2 March 2012–23 July 2014 (n = 853)*. *Where the month of onset is unknown, the month of reporting has been used.ECDC line listing: data compiled from WHO and Ministries of Health websites around the world.

Figure 3

Density of Camelidae, Number of Camelidae per 1000 inhabitants and MERS‐CoV identification in camels as of 23 July 2014.The map was created using data from: World Health Organisation for Animal Health. World Animal Health Information Database (WAHID), Animal population, Camelidae, 2011–2013, Available from http://www.oie.int/wahis_2/public/wahid.php/Countryinformation/Animalpopulation. Surface area and human population: World Bank, 2009–2013. http://data.worldbank.org/. References: (Perera et al., 2013; Reusken et al., 2013a,b; Alagaili et al., 2014; Corman et al., 2014; Meyer et al., 2014).

Figure 4

Density of Camelidae in the Arabian Peninsula and number of MERS‐CoV human cases between 2 March 2012 and 23 July 2014 (n = 695*). *Cases for which probable region of infection is available.The map was created using data from: World Health Organisation for Animal Health. World Animal Health Information Database (WAHID), Animal population, Camelidae, 2011–2013, Available from http://www.oie.int/wahis_2/public/wahid.php/Countryinformation/Animalpopulation. ECDC line listing: data compiled from WHO and Ministries of Health websites around the world.