Scientists say that that Middle East respiratory syndrome coronavirus (MERS-CoV) is likely to have been transmitted from animals to humans on more than one occasion, according to a new study published in The Lancet.
The largest study of MERS-CoV so far has been conducted by researchers from the Saudi Arabian Ministry of Health, University College London (UCL) and UCL Partners, and the Wellcome Trust Sanger Institute.
The researchers used advanced DNA analysis techniques in order to analyze the MERS-CoV genomes taken directly from 21 patients with MERS from different regions of Saudi Arabia.
The researchers say the techniques meant they were able to “reconstruct” where, when and how the virus has evolved.
This allowed them to determine whether the virus stemmed from one incidence of the virus passing from animal to human with subsequent transmission between humans, or whether the virus is passing between animals and humans repeatedly.
From their research, the scientists found that the virus appears to center around the Riyadh area of Saudi Arabia “with sporadic excursions to other areas.” But the researchers note that further research will be required to further determine exact locations involved.
From this, the scientists found that it appears the MERS-CoV virus has transmitted from an “animal reservoir” to humans on several occasions and has continued to transmit between humans thereafter.
The researchers say that diverse genetic variants of the virus have appeared in Riyadh. They add that this “high local diversity may indicate that the virus is being transmitted from an animal reservoir which is being continuously imported from other regions.”
However, they note that it could be attributed to the fact that Riyadh has the largest populated center, meaning it is a bigger target for human-to-human transmission.
Additionally, their findings showed that it has been a long time since the virus has shared a common ancestor. The scientists note that this may indicate the MERS-CoV may be transmitted by an “intermediary animal host.”
Signs of MERS-CoV have previously been found in bats, and Medical News Today recently reported on a study suggesting that camels could be a carrier of the virus.
However, the researchers say there has been no definitive animal reservoir identified for the virus as yet, therefore further research is required.
Ziad Memish, of the Saudi Arabian Ministry of Health and study author, says:
“So far, there has been very little information about the molecular evolution of MERS-CoV, and how this relates to virus transmission.”
“While our research substantially adds to the existing evidence base for how, where, and when MERS-CoV is transmitting, further definition of the exposures responsible for the sporadic introductions of MERS-CoV into human populations is urgently needed to provide the necessary information to interrupt transmission and contain the virus.”
Alimuddin Zumla of UCL notes that in light of the study’s findings and the fact that the source of MERS-CoV has not yet been found, it appears that the transmission of the virus is more complicated than originally anticipated.
He says, however, that although there have been many mass gatherings throughout Saudi Arabia in the last 12 months, it is positive that there have been no major outbreaks of the MERS-CoV reported from these events.
“Watchful surveillance and vigilance is required despite the minimal risk of global spread,” he adds.
In a linked article following the study, David SC Hui of the Chinese University of Hong Kong notes that molecular methods in tracing emerging severe acute respiratory infections, such as those used in this study, have proved useful in the past.
He points to the severe acute respiratory syndrome (SARS) coronavirus outbreaks in 2003, where diagnostic blood RNA assays were successful in early detection of the virus.
“These quantitative systems, if available, might be useful for the early diagnosis of MERS-CoV and can provide viral load information that might facilitate prognostic assessments of an infected individual,” he adds.
“Development of rapid and reliable diagnostic assays is urgently needed so that health authorities can take appropriate public health measures to interrupt disease transmission and contain the virus.”