Are bats sources of the novel Wuhan coronavirus epidemic?

Autors: Emily Clayton and Muhammad Munir

Molecular Virology, Biomedical and Life Sciences, Lancaster University, Lancaster UK

The novel 2019 coronavirus (2019-nCoV) outbreak originating from Wuhan in China is now progressing further, with more than 9,000 confirmed cases and according to Chinese officials, over 213 deaths. Two cases of the coronavirus have now been identified in the UK where two members of the same family have tested positive for the virus. The coronavirus has already spread to many other countries including Thailand, Hong Kong, South Korea, Malaysia, Japan, France, Canada, Vietnam, Cambodia, Nepal and Germany. No deaths have yet been reported outside of China. The World Health Organisation (W.H.O) have now decided to declare the coronavirus outbreak as a global public health emergency.

This is not the first time we have seen an epidemic coronavirus outbreak. The Wuhan 2019-nCoV appears to be very similar to the Severe Acute Respiratory Syndrome (SARS) outbreak that occurred in 2002-2003 where the majority of cases also occurred in China. Symptoms of the Wuhan novel coronavirus include feeling tired, difficulty breathing, high temperature, coughing and other respiratory symptoms as it is thought that this virus targets the lungs and the respiratory tract, which if not managed can lead to infections and pneumonia. Because this is a new virus it is not yet known exactly how it spread from person to person but similar viruses are spread via cough droplets either directly or from contaminated objects. There is no specific treatment for the virus, instead healthcare professionals aim to alleviate the symptoms of those infected.

The 2019-nCoV originated from a seafood market in the centre of Wuhan where trading of abundant animal meats takes place. The market has now been closed down and the whole of Wuhan has been contained as an essential measure to prevent the spread of the virus. Like other coronaviruses, this novel coronavirus is zoonotic, meaning that the virus has originated in animals and spread from animals to humans. A study by The Lancet analysed 10 genome sequences of the 2019-nCoV taken from 9 patients in China and compared them to a viral sequence library. Results showed that the most closely related viruses were two coronaviruses that were originated from bats, sharing 88% of the same genetic sequence. It can hence be determined that this novel coronavirus is likely to have originated from bats. Investigations found that bats were not being traded as meat in the seafood market where the outbreak stemmed from; therefore, another unknown animal intermediate has facilitated the transmission of the coronavirus from bats to humans. The 2019-nCoV has been determined as sufficiently different to the SARS-CoV and is to be considered as a new human-infecting coronavirus.

Bats possess the unique ability to host many viruses without getting sick, yet they can still transmit the virus into susceptible hosts such as humans in which the virus is highly pathogenic. Bats have been recognised as a reservoir for many viruses including Ebola, Rabies, Nipah and significantly, bats were responsible for the SARS coronaviruses. Bats are extremely diverse and account for a quarter of all mammalian species and are found in all continents except Antarctica. The ability of bats to co-exist with viruses without showing any symptoms of infection is hypothesised to be due to their unique characteristics and immune system. Bats are the only flying mammal and can travel over very large distances when migrating. They live in large groups and have a very long lifespan for such a small mammal, with some bats living for up to 40 years. All of these factors appear to encourage the likeliness of viral transmission between bats and also to other animals. Spillover of viruses from bats into other animals can then affect human populations when we eat them, trade them as livestock and live in their territories. SARS was a zoonotic coronavirus whose outbreak originated from bats and was then passed onto humans via intermediate animal hosts such as racoons, civet cats and dogs.

Researchers in China had previously predicted that the bat-borne coronaviruses will remerge to cause the next outbreak, which proved to be correct. Despite these predictions, there was little done to prevent this epidemic from occurring both in and out of the public eye, as it was not presented as a pressing issue until now. The Wuhan 2019-nCoV outbreak now highlights the importance of investigating bats and other animal hosts as hidden viral reservoirs and proves a need in understanding their potential to allow spill over into human populations where the virus causes devastating effects. There is also the need to stop the sale of certain wildlife in markets to prevent future outbreaks.

Measures to limit the spread of the 2019-nCoV are being put in place, such as the containment of the city of Wuhan; preventing people entering and leaving the city will hopefully reduce the spread of the virus to the rest of China. General hygiene practices are being highly enforced to residents in China to ensure that they do not catch the virus from other people. Countries such as the USA and Japan are now halting flights to and from Wuhan in an aid to prevent the spread of the 2019-nCoV globally. Furthermore, it has been proposed that coronavirus patients remain highly infective even after death. Therefore, careful measures are taking place in China when handling patients bodies to ensure that the virus is not passed on to the healthcare professionals treating them or to any others who may come into contact.