Source: https://sphcm.med.unsw.edu.au/news/could-mers-coronavirus-be-bioterrorism-new-study-shows-why-could-be-one-explanations-paradoxes
The MERS Coronavirus (MERS Co-V) emerged in 2012 and continues to cause illness and death more than 2 years later. It has been compared to SARS, which caused a pandemic more than 10 years ago, and public health response to MERS-CoV has been modeled on the response to SARS.
Australian Infectious diseases epidemiologist Professor Raina MacIntyre from The School of Public Health And Community Medicine at UNSW, analysed the epidemiologic features of MERS-Cov compared to SARS and shows that it is very different to SARS in a new study, published today in Environment Systems and Decisions (http://link.springer.com/article/10.1007/s10669-014-9506-5/fulltext.html). Many of the features are paradoxical and cannot be explained by known principles of epidemiology. For example, despite outbreaks in hospitals, MERS-CoV was present in several mass gatherings such as the Hajj pilgrimage, and did not result in an epidemic. SARS, which was estimated to be more infectious than MERS-CoV, caused a classic epidemic of over 8000 cases globally and was eliminated from the human population within 8 months. MERS-CoV on the other hand, estimated to be less infectious, has persisted for more than 3 times the duration of SARS. Further, SARS causes satellite epidemics in countries to which it spread, whereas MERS-CoV has remained mainly in the Middle East, without sparking epidemics in other countries where cases have occurred.
In SARS, outbreaks in hospitals were caused by a single strain, but with MERS-CoV, more than one strain of the virus has been identified in some outbreaks. This means that people hospitalized with MERS-CoV or who developed the infection in hospital were exposed to several different viruses at around the same time. Where did these viruses come from? What was the source of infection to humans?
“It is a mystery why this virus, which has low apparent infectiousness has persisted for so long when a consistent source of infections has not been identified.” says MacIntyre. “Infections cannot materialize from thin air. Human beings are being infected from a source, either other humans or a non-human source. A non-human source could be an animal source or deliberate release.”
There is evidence for camels as a source, with a few cases having contact with camels, but many human cases have no known contact with camels or other animals. “The finding of the virus in camels,” says MacIntyre, “does not exclude bioterrorism as a cause. A virus that has a trophism for particular animals, when present in an environment, will tend to infect those animals. It’s a case of which came first, the chicken or the egg.”
The other postulated explanation for the paradoxes of MERS-CoV is that there are many mild or asymptomatic cases which have gone undetected. However, attempts to look for such cases has not turned up high numbers of mild or asymptomatic cases. Whether this is the explanation will become clearer as better screening methods are developed.
Professor MacIntyre fitted the observed features of MERS-CoV to an epidemic pattern and two sporadic patterns – an animal source or deliberate release. The pattern was much more consistent with a sporadic source, with slightly more weight to deliberate release than an animal source, although both are possible.
“It could be either explanation. In the case of bioterrorism, if it is not considered at all, it can never be detected, unless it involves an eradicated pathogen such as smallpox” says MacIntyre. “In public health we are generally not good at interpreting aberrant patterns. A good example is the Rajneesh salmonella attack in 1984 in the US – public health authorities did not consider the possibility of bioterrorism, despite a local politician arguing the case that it might be bioterrorism, and despite the facts not fitting with ordinary food poisoning. If Rajneesh had not confessed later, the attack would have never been recognised, and even when he did confess, he wasn’t believed. This case illustrates normal human tendency to force available facts into common, confortable explanations, rather than to view the facts objectively.”
“The patterns of MERS-CoV are unusual, and whilst an animal reservoir or undetected mild human cases as the source of ongoing human infections are both possible, the possibility of bioterrorism should also be considered, because the data fit this explanation. In the case of deliberate release, simulating nature would be difficult with a sporadic infection, and this may explain the observed discrepancies in the epidemiology.”
“Whatever the source of persistent MERS-CoV infections, using a framework based on SARS to tackle this infection is a mistake, because it is very different to SARS.”
See commentary on Prof MacIntyre’s Infectious Diseases FB page: https://www.facebook.com/ProfRainaMacIntyre?focus_composer=true&ref_type=bookmark
See Conversation comment: https://theconversation.com/mers-coronavirus-animal-source-or-deliberate-release-29690#comment_431898
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