Novel Corona Virus (MERS): The Unknown Vector

Novel Coronavirus 2012 (nCoV), Human Coronavirus-Erasmus Medical Center (hCoV-EMC) SARS-2 or MERS, the tentative name of this recently discovered Corona Virus, now seems to be able to spread from human to human. But where did it originate?

The first known cluster of MERS occurred in April 2012 in Jordan, while the second occurred a few months later in Saudi Arabia. Were these cases related?

The genomic structure of this deadly virus has been determined and the virus seems[1] very similar to those reported for bats-derived Coronaviruses of the 2c subgroup: the Bat-CoV HKU4 and HKU5 stains. Research has also demonstrated that Corona viruses have the potential to undergo rapid genetic change as they adapt to new hosts[2].

[Asellia tridens. Foto: Lars Bjurström]

Bats are being increasingly recognized[3] as an important reservoir of zoonotic viruses of different families, including Coronaviruses, Nipah virus, Hendra virus and Ebola virus. At least 27 species of bats are known to live in Jordan, while more than 29 species of bats have so far been identified in Saudi Arabia.

Thus the question remains how the virus managed to jump from bats to humans. The unknown vector seems elusive but the answer may be easy: mosquitoes.

[Foto: Paul Zborowski]

Mosquitoes are insect vectors responsible for the transmission of parasitic and viral infections to millions of people worldwide, with substantial morbidity and mortality. Infections transmitted by mosquitoes include malaria, yellow fever, chikungunya, dengue, West Nile virus, and other arboviruses. They infect mammals, like bats and humans. Several of these viruses have been isolated from both bats and humans[4].

This could indicate that mosquitoes could first feed on the blood of an infected bat and when it subsequently feeds on the blood of a human, it will infect the human with Coronavirus.

[1] Lu et al: SARS-like virus in the Middle East: a truly bat-related coronavirus causing human diseases in Protein & Cell - 2012 
[2] Rest et al: SARS associated coronavirus has a recombinant polymerase and coronaviruses have a history of host-shifting in Journal of molecular epidemiology and evolutionary genetics in infectious diseases - 2003
[3] Smith et al: Bats and their virome: an important source of emerging viruses capable of infecting humans in Current Opinion in Virology - 2013 
[4] Paessler et al: Pathogenesis of the viral hemorrhagic fevers in Annual Review of Pathology – 2013