Credit Dr Ian Mackay VDU Blog
# 8538
The sudden spike in MERS virus detections in Saudi Arabia and the UAE over the last month has sparked a good deal of concern that the MERS coronavirus might be evolving into a more human-adapted virus. While not the only possible explanation for this increase - it would be the most worrisome - were it true.
On Friday (see Referral: VDU Blog On MERS-CoV Partial Spike Sequence Results), Dr. Ian Mackay explained the early results of genetic testing performed by Christian Drosten’s lab in Germany on MERS samples gathered from the recent Jeddah outbreak, which found no changes to the spike protein region of the virus.
A good sign that the virus was relatively unchanged, but as only a subset of MERS genome was examined, not definitive.
Yesterday evening news began to emerge that Dr. Drosten had fully sequenced three virus samples from the Jeddah outbreak, and that these samples showed `no significant changes’ compared to earlier samples sequenced.
A finding that would appear to remove the `easiest’ explanation for these recent outbreaks from the top of the suspect list.
Dr. Ian Mackay posted a short announcement last night on his VDU blog, which he later updated, along with a second post where he discusses the ramifications of this finding, along with a small but important caveat (note: the `curve’ mentioned refers to his graphic at the top of this post).
If this is what MERS-CoV detections look like with more testing...what is the "normal" community level of virus?? [UPDATED]
For a virus that is chugging along without the aid of any new genetic changes, and perhaps showing up more often (a) because of enhanced testing and/or (b) because of a large-scale breakdown in infection prevention and control (IPC), this curve sure does depict the possibility that we had no idea how much MERS-CoV was transmitting among the population. Still a poor transmitter compared to an influenzavirus, because we have seen a few larger MERS-CoV studies than show few to no MERS-CoV positives, but still more people positive than we thought.
Then `minor caveat’ here is that these three comparative samples came from early in the Jeddah outbreak, which doesn’t preclude the possibility that some evolutionary changes may have occurred since then. But the most likely explanation at this point would involve something other than an adaptation of the virus.
Dr. Drosten wrote a letter to ProMed Mail, outlining his findings, which appeared overnight. A brief excerpt follows:
MERS-COV - EASTERN MEDITERRANEAN (42): SAUDI ARABIA, GENOME SEQUENCING, JEDDAH OUTBREAK
A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org
Date: Sat 26 Apr 2014
From: Christian Drosten <drosten@virology-bonn.de> [edited](EXCERPT)
We have sequenced near full genomes of 3 viruses from the early phase of the Jeddah outbreak. The samples were submitted to Jeddah regional laboratory on [3, 5 and 7 Apr 2014], and sent to Germany for external confirmatory testing on [14 Apr 2014] by KSA MOH in Riyadh. Two of the sequenced viruses were from patients treated in the major public hospital in which most cases of the Jeddah outbreak seem to have occurred. A 3rd sequence was from another health care facility in the city.
Genome sequences of all 3 viruses are highly similar to each other but not identical, and are highly similar to a large number of known MERS-CoV sequences (consult http://www.virology-bonn.de for a phylogeny; genome overview in Cotten 2014). There are no genome insertions or deletions suggestive of sudden major changes. The receptor-binding domain in the spike protein thought to influence the virus's ability to be transmitted or spread is 100 percent identical to the binding site in a large number of known MERS-CoV genome sequences. Based on genome comparison with other MERS-CoV strains there is no reason to assume that the sequenced viruses from Jeddah have acquired changes increasing their pandemic potential.
To this cavalcade of coverage we can add Helen Branswell’s excellent report for the Canadian Press:
MERS virus hasn't changed, not reason for surge in Saudi cases: expert
Helen Branswell / The Canadian Press
April 26, 2014 05:36 PMA German coronavirus expert says the virus responsible for the MERS infection appears not to have changed.
Dr. Christian Drosten says based on what his laboratory has seen so far, this month's surge in MERS cases cannot be explained by mutations in the virus.
Drosten's lab at the University of Bonn has been looking at genetic sequences of RNA drawn from samples from 30 recent cases from Jidda, Saudi Arabia, where the largest increase in cases has occurred.
In an email, Drosten says the lab has sequenced three nearly full genomes and they see no signs of significant changes that could account for the increase in cases.
As far as what the actual reason for the recent spike in MERS cases might be, it will likely require good old-fashioned gumshoe epidemiology to figure that out.
An investigation that would include, but not be limited to: extensive contact tracing, broad viral (rRT-PCR) & serological testing, a review of infection control protocols, and a long-promised but never-delivered Case Control Study to determine what specific exposures are most likely to lead to infection.
Basic investigative steps that should have been implemented by Saudi Arabia well over a year ago, and that hopefully with a new Minister of Health in charge, will now get top priority.
