Discussion around the covid-2019 outbreak has focused on city lockdowns and how best to control the virus.1-3 But we should not ignore the protection of wild animals and their part in this pandemic.
Results from early investigations into the virus outbreak in Wuhan, Hubei Province, suggest that Huanan seafood market, which closed on 1 January 2020, might be the source of the infection. Of the first 41 patients, 27 had been exposed to the market.3,4 Further studies found that among 585 samples collected from both the environment and the animals from Huanan seafood market and other markets, 33 tested positive for covid-2019. Thirty one of these samples were from the part of the market where wild animals were traded, suggesting that the outbreak could be related to these transactions.5-6
Wild animals are the reservoir for numerous viruses. Bats, for example, carry many diverse coronaviruses, including those similar to the coronaviruses responsible for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).7 These viruses are then spread to humans by way of an intermediate species. In 2003, the coronavirus that caused SARS spread from bats to humans through civet cats as the intermediate species.8-10 The MERS coronavirus spread from bats to humans through dromedary camels.11
Studies show that the coronavirus responsible for covid-2019, SARS-Cov-2, is closely related (88% identity) to two bat derived SARS-like coronaviruses, bat-SL-CoVZC45 and bat-SL-CoVZXC21, that were collected in Zhoushan city, eastern China, in 2018.12 Snakes were once suspected as the intermediate hosts but this hypothesis was dismissed.13 One study found that the genetic sequence of viruses isolated from pangolins in Guangzhou city, China, is 99% similar to that of SARS-Cov-2 isolated from patients, suggesting that the pangolin is the likely intermediate species.14
How a bat derived virus from Zhoushan in Zhejiang Province reached Wuhan and Guangzhou, at distances of more than 1000 km and 1400 km apart, respectively, remains to be established. Similarly, the SARS virus was originally found in cave bats in the remote mountain region of Yunnan Province, whereas the disease outbreak began in Guangzhou, a distance of more than 1600 km.8
Another question is why zoonoses seem to occur more often in China than elsewhere. Numerous explanations are possible, although several factors are most important.15-16 Firstly, China has a long history and tradition of eating wild animals – some people believe that wild animals are more nutritious than domesticated or farmed animals. The rarer or harder an animal is to obtain, the more valuable and nutritious it seems. By that logic, bird’s nests from a high mountain peak or bear’s feet are most nutritious. This way of thinking increases the demand for wild animals for food and does not take into account that animals can spread viruses.
Secondly, the current wildlife protection law in China aims mainly to protect most endangered wild animals. Hence, less endangered wild animals are insufficiently monitored and only a small number of wild animals are protected by law. Wild animals are captured to be sold and eaten, and there are many opportunities for people to interact with them and become infected.
The law allows, and to some extent encourages, people to use wild animals as a way of getting out of poverty and to become rich by domesticating them. Apart from the risk of infection when capturing a wild animal, it is difficult to police the market because it is hard to differentiate domesticated wild animals from those captured from their natural habitat.
Wild animals, such as civet cats and pangolins, are sold in Chinese markets and play a role as the intermediate host for viruses. To avoid similar situations to that of SARS and covid-2019, these intermediate hosts should be left alone, the rights of wild animals respected, and a ban imposed on removing animals from their natural habitat to be sold on the open market. This is the right way to protect ourselves from novel viruses. Encouragingly, in response to the ongoing emergency, the Chinese National Congress is establishing a new law for the stricter protection of wild animals.17
Mei-Mei Wang, PhD candidate, Infection Prevention and Control Center, Xiang-Ya Hospital, Central South University, China.
An-Hua Wu, Professor, Infection Prevention and Control Center, Xiang-Ya Hospital, Central South University, China.
Chang-Qing Gao, Associate Professor, Infection Prevention and Control Center, and Center for Study in Laboratory Animals, Xiang-Ya Hospital, Central South University, China.
Corresponding author: CQ Gao email@example.com
The research in the laboratory of the authors is supported by a grant from the National Basic Research Program of China [2017YFA0105201].
- Horton R. 2019-nCoV—A desperate plea. Lancet 2020;395:400.
- Rubin GJ, Wessely S. The psychological effects of quarantining a city. BMJ 2020;368:m313. doi: 10.1136/bmj.m313.
- Anon. COVID-19: fighting panic with information. Lancet 2020;395:537.
- Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497-506.
- Li Q, Guan X, Wu P, et al. Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia. N Engl J Med 2020; doi:10.1056/NEJMoa2001316.
- The State Council joint prevention and control mechanism press conference.
- de Wit E, van Doremalen N, Falzarano D, et al. SARS and MERS: recent insights into emerging coronaviruses. Nat Rev Microbiol 2016;14:523-34.
- Ge XY, Li JL, Yang XL, et al. Isolation and characterization of a bat SARS-like coronavirus that uses the ACE2 receptor. Nature 2013;503:535-8.
- Cyranoski D. Bat cave solves mystery of deadly SARS virus – and suggests new outbreak could occur. Nature 2017;552:15-16.
- Hu B, Zeng LP, Yang XL, et al. Discovery of a rich gene pool of bat SARS-related coronaviruses provides new insights into the origin of SARS coronavirus. PLoS Pathog 2017;13:e1006698.
- Alagaili AN, Briese T, Mishra N, et al. Middle East respiratory syndrome coronavirus infection in dromedary camels in Saudi Arabia. mBio 2014;5: e00884-e00914
- Lu R, Zhao X, Li J, et al. Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding. Lancet 2020; 395:565-74.
- Callaway E and Cyranoski D. Why snakes probably aren’t spreading the new China virus. Nature. News. 23 Jan 2020
- David C. Did pangolins spread the China coronavirus to people? Nature 2020
- Ke Z, Hou JR. Improve the law of wildlife protection, prevent and control the spread of infectious diseases. Legal Daily—Legal Network.
- Li YS. Organize a network of laws and regulations to crack down on the market and trade of illegal wild animals. China discipline inspection and supervision report.
- Decision of the Standing Committee of the National People ‘ Congress on the banning illegal wildlife trade in an all-round way, getting rid of the bad habit of eating wild animals and ensuring the life, health and safety of the people.