A recently discovered virus could be the next deadly epidemic in humans. Middle East Respiratory Coronavirus, or MERS-CoV for short, was isolated from a patient in Saudi Arabia in March of 2012 and has since been implicated in deaths across the region. While the virus has been a hot topic of research over the past year, with at least 63 papers published, epidemiologists have only recently characterized the possible extent of human transmission and mortality. In a paper published in Lancet on November 13, researchers attempted to give a comprehensive look at how virulent the disease may be.
What is a coronavirus?
The Center for Disease Control states that coronaviruses are one of the most common types of virus worldwide and that most people will be infected by one at some point in their life. They can be transmitted from human to human or between animals and humans and are usually more irritating than deadly. This is certainly not always the case however; in those who are immunologically compromised, coronaviruses can cause symptoms as severe as pneumonia. The most well-known example of a coronavirus is SARS, which caused over 700 deaths at the beginning of the 21st century. Several papers have drawn comparisons between MERS-CoV and SARS, and many fear that the new pathogen could cause a deadly outbreak if public health measures are not utilized appropriately.
What we know about MERS-CoV
Despite being the focus of a relatively high number of papers, our knowledge of MERS-CoV is somewhat limited. The exact method of transmission of the virus has not been determined, although camels and bats are both believed to be reservoirs. The majority of cases have been confined to the Middle East, and especially Saudi Arabia, however infections in the UK, France, and Tunisia have been linked back to travel in the region. Although discovered fairly recently, MERS-CoV has been implicated in at least 111 cases as of August 2013. Of these 111 cases, 46 were fatal. While the high number of fatalities is shocking, researchers estimate that there have likely been at least 940 cases, the majority of which have gone unreported.
The study in Lancet sought to compile a comprehensive database of all the reported cases thus far in order to learn more about the virulence of the virus. The authors found that the virus is significantly more deadly in patients over 50, with 77% of cases ending in fatality compared to 22% for those under 50. They looked at animal-human and human-human transmission models and determined that visitors to the Middle East were at a higher risk of transmission from reservoir animals than locals. The most significant finding from the database was that the value of R for MERS-CoV was slightly above 1 but could be decreasing. This means that transmission is not 1-1 and therefore self-sustaining, but it is close. Given how incomplete the current data on MER-CoV is, the researchers estimate that R may have already dropped below 1. More cases must be observed before it can be conclusively determined how quickly the virus spreads, however it is likely already at epidemic status.
What this means for us
Although MERS-CoV is deadly, few cases have been reported outside of the Middle East and none of them have occurred in the United States. If researchers are correct that the majority of cases have gone unreported, it is also likely that many of these cases are mild and do not lead to death or even hospitalization. Furthermore, a pharmaceutical company recently announced that they had begun clinical testing of a vaccine to the virus. If the vaccine is successful and combined with a robust public health program, it is possible that MER-CoV could be contained before it spreads much further. Ultimately though, it is necessary for research to continue and for the public to be aware of the virus as tourists to the Middle East could potentially spread the disease across the world.
The study in Lancet – thelancet.com/pdfs/journals/laninf/PIIS1473309913703049.pdf?id=8b69abadd6dadf97:4d51d508:14292206b53:-6e951385431584619
CDC Information on coronaviruses – http://www.cdc.gov/coronavirus/about/index.html