Between November 2002 and July 2003, a novel respiratory virus appeared in South China, spreading first to Hong Kong and going on to infect people in 37 countries around the world. As the virus spread, thousands were quarantined, schools were shut, and many airports implemented thermal screening programmes to stop potentially infected people from getting on planes. By the end of the pandemic, the Severe Acute Respiratory Syndrome (SARS) coronavirus (SARS-CoV) had resulted in 8,273 cases and 775 deaths, a case fatality rate of 10%.
So it’s not surprising that many are now nervous after the World Health Organisation (WHO) reported that a novel coronavirus (nCoV), closely related to the SARS virus, has emerged in the Middle East. Since early 2012, there have been 34 confirmed cases of infection with nCoV, which causes severe acute pneumonia and renal failure. With 18 deaths so far, the case fatality rate currently sits at over 50%, a frightening statistic. But is this new coronavirus going to go pandemic, like the SARS virus did? With such a small number of cases to date, it is too early to say for sure.
In 2002/2003, the SARS virus spread rapidly, infecting otherwise healthy individuals. It arrived in Hong Kong via a mainland doctor who stayed at a hotel in Kowloon. He infected 16 of the hotel visitors, who themselves traveled on to Canada, Singapore, Taiwan, and Vietnam, taking SARS with them.
In contrast, the majority of nCoV cases have remained within Saudi Arabia and while there have been cases exported to Jordan, Qatar, the United Arab Emirates, the United Kingdom and France, the virus does not seem to have spread much beyond the index cases. There have been a small number of cases of family members becoming infected. This confirms that nCoV can transmit from person to person but suggests that prolonged exposure is needed to become infected, at least for healthy people.
One of the interesting features of this novel coronavirus, is that the majority of infections have occurred within health care facilities. The most recent cluster of cases within Saudi Arabia have occurred within a single facility and all patients had at least one other underlying disease. Furthermore, the Ministry of Social Affairs and Health in France has just informed the WHO of a confirmed case of nCoV in a patient who spent three days sharing a hospital room with France’s first nCoV patient. These cases suggest that underlying diseases may also make people more vulnerable to infection with nCoV.
So far, the evidence is suggesting that nCoV is unlikely to turn into a pandemic. But the thing about viruses is that you never know. What we do know is that nCoV is highly infectious to human airway epithelial cultures in the laboratory, and that the virus can hide itself from the human immune system (1). But somehow this isn’t currently translating into epidemic spread out in the real world. But we shouldn’t be complacent. It is certainly not inconceivable that nCoV could mutate in some way to become more infectious to healthy people, the first step towards a SARS-like scenario. And there is still so much we don’t know about nCoV. Where did it come from? What is nCoV’s natural reservoir? In the case of SARS, the virus was found in samples of wild animals sold as food in the local markets, many of which show no clinical signs of infection. So far, there is limited information on any potential links between nCoV cases and exposure to animals, although nCoV is closely related to coronaviruses from bats (2).
If nothing else, though, the emergence of nCoV is another warning of the threat we face from novel viruses. As many of these viruses cross over to humans from wild animals, these threats are going to increase as humans continue to encroach on the natural habitats of so many creatures. And our interconnected global world means any virus is less than 24 hours from anywhere else on earth. A sobering thought.
1. Kindler E, Jónsdóttir HR, Muth D, Hamming OJ, Hartmann R, Rodriguez R, Geffers R, Fouchier RAM, Drosten C, Müller MA, Dijkman R, Thiel V. 2013. Efficient replication of the novel human betacoronavirus EMC on primary human epithelium highlights its zoonotic potential. mBio 4(1):e00611-12. doi:10.1128/mBio.00611-12.
2. van Boheemen S, et al. 2012. Genomic characterization of a newly discovered coronavirus associated with acute respiratory distress syndrome in humans. mBio 3(6):e00473-12. doi:10.1128/mBio.00473-12.