A study published in the Centers for Disease Control and Prevention journal Emerging Infectious Diseases by Memish et al. analyzed the presence of coronaviruses (including MERS-CoV) in 1.003 samples from wild bats collected in October 2012 and April 2013 in Saudi Arabia.
Samples were collected in Bisha, Saudi Arabia, close to where the first patient with MERS-CoV was identified in September 2012 and in other regions where MERS-CoV cases have been found. Multiple alpha and beta coronavirus sequences were identified in 220 out of 732 roost feces samples and seven of 91 rectal swab samples or fecal pellets.
One amplified sequence of MERS-CoV from a T. perforatus bat captured in October 2012 in Bisha matched 100% with the MERS-CoV cloned from the index case-patient in Bisha. The authors conclude that bats might play a role in human infection although this does not exclude the possibility of other hosts.
ECDC comment, 26 August 2013:
Identifying the host/s and source of MERS-CoV is urgently needed to prevent further infections and spread of the disease. Bat species are a well-known reservoir of coronaviruses and the study of Memish et al. confirms this.
While the results from the study are intriguing, there are several limitations that might limit a conclusion that bats are the direct source of MERS-CoV in humans.
In this study a total of 1,003 different samples were collected from 110 bats captured during two samplings (October 2012 and April 2013); of those 227 samples tested positive for coronavirus, only one was found positive for the human MERS-CoV. The information about the viral load of the MERS-CoV positive sample is missing and the failure of further sequencing might lead to the speculation of a very low virus load in the sample.
The amplified bat MERS-CoV sequence was very short and lies within a conserved region of the genome, however a divergence within other genomic regions cannot be ruled out.
Furthermore the MERS-CoV sequence amplification product of this positive sample was retrieved only from newly established generic MERS-Coronavirus (nested RdRp) assay, while the World Health Organization recommended MERS-CoV specific assays were negative.