2019 nCoV in context: lessons learned?
The emergence of a new coronavirus (2019 nCoV) in Wuhan creates a sense of deja vu with the severe acute respiratory syndrome coronavirus (SARS CoV) epidemic in China in 2003. Coronaviruses are enveloped, positivestranded RNA viruses of mammals and birds. These viruses have high mutation and gene recombination rates, making them ideal for pathogen evolution. In humans, coronavirus is usually associated with mild disease, the common cold. Previous emerging novel coronaviruses, such as SARS CoV and Middle East respiratory syndrome coronavirus (MERS CoV) which emerged in the Middle East in 2012, were associated with severe and sometimes fatal disease. MERS CoV was less pathogenic than SARS CoV, with the most severe infections mainly in individuals with underlying illnesses. Clinically and epidemiologically, the contemporary 2019 nCoV in China seems to resemble SARS CoV. The genome of 2019 nCoV also appears most closely related to SARS CoV and related bat coronaviruses. The infection has now spread widely, with phylogenetic analysis of the emerging viruses suggesting an initial single locus zoonotic spillover event in November, 2019, and subsequent humanto human transmission. The SARS epidemic in 2003 was followed soon after by avian influenza H5N1 in 2006, centred on the Asian continent and Middle East. Other surprising viral zoonoses that have caused serious disease include Nipah encephalitic virus in pigs and humans in southeast and south Asia in 1999 2014, and large scale Ebola virus epidemics in 2014 16 and 2018 19 in west and central Africa. Taken together, these events ring alarm bells about disease emergence in the 21st century, and the importance of human diseases originating from indiscriminate contacts with infected animals. There is an increasing focus on the human animalenvironment disease interface, as encompassed in the One Health concept. Mortalities, disability adjusted life years, and billions of dollars of economic losses from these infections demand action and investment in prevention to face novel challenges to human and animal health. Research has led to better understanding of the nature and drivers of cross species viral jumps, but the detail is still elusive. No reservoir population of bats for SARS and MERS CoV or Ebola virus have been definitively identified, despite considerable searching, possibly because of the source virus circulating in small and isolated populations. Forensic examination has clarified the human infection sources and multispecies involvement in these diseases, with some species confirmed as competent hosts (eg, camels for MERSCoV) bridge (or amplifying) hosts (eg, pigs for Nipah virus, non human primates for Ebola virus) or deadend hosts. The crucial checkpoint is the jump and bridging of the viruses to humans, which occurs most frequently through animal based food systems. In the case of SARS, markets with live and dead animals of wild and domestic origins were the crucible for virus evolution and emergence in the human population. Once the viruses' functional proteins enabled cell entry in civets (Paguma larvata) and racoon dogs (Nyctereutes procyonoides) the bridge was established and it was only a matter of time before the jump to humans occurred. Sequence comparison of civet viruses suggested evolution was ongoing; this was further supported by high seroprevalence of antibodies against SARS CoV among civet sellers, suggesting previous cross species transmission events without necessarily human tohuman transmission. Similarly, early Ebola virus was mostly associated with bushmeat and its consumption in Africa; Nipah virus is associated with date palm sap, fruit, and domestic pig farms; MERS is associated with the camel livestock industry; and H5N1 arose from viral evolution in domestic and wild birds, to ultimately bring all these cases to humans. The 2019 nCoV is another virus in the pipeline that originated from contact with animals, in this case a seafood and animal market in Wuhan, China. Inevitably, the health sectors are primarily reactive to these events, acting to save lives as well as undertake surveillance and control. The drama and panic typically fade into history with the substantial costs being absorbed by ordinary people, international financial systems, and tax bases, making life go on as normal, but not quite. The frequency, severity, and financial impacts of these events are growing, and the world can no longer afford to just wait and see, especially because prevention of these threats is in theory relatively simple and where addressed has resulted in a cessation of risk. The best example being Nipah virus, where separation Lancet Planet Health 2020
The Lancet Planetary Health