The novel coronavirus that has claimed over 400 lives and infected thousands in China may have originated from Bats, according to two latest studies published in the journal Nature on February 3.
The first study found that the virus was closely related to a group of SARS-like coronaviruses previously identified in bats in China, reports economic times.
The coronavirus outbreak, which originated in the central Hubei province in December, killed over 400 with 57 deaths reported on February 2, while the number of confirmed cases has climbed to 20,438.
The Philippines on February 2 reported the first death outside China from the epidemic that has spread to 25 countries, including India, US, UK and Russia.
In China, all the deaths have been reported in Hubei Province - the epicentre of the virus outbreak. The virus was declared a global health emergency by the World Health Organisation (WHO) on January 31.
The first patient was admitted to a hospital on December 12 last year, and investigations have identified a seafood market, which also sold wild animals, in Wuhan, capital of Hubei, as the potential source of the outbreak.
Doctors from Fudan University in China studied the 41-year-old male patient on December 26, who experienced symptoms of respiratory illness, including fever, chest tightness and cough.
A combination of antibiotic, antiviral and glucocorticoid therapy was administered. However, the patient exhibited respiratory failure and his condition did not improve after three days of treatment.
The researchers performed genome sequencing on a sample of bronchoalveolar lavage fluid - a lung secretion - collected from the patient.
They identified a novel virus and found that the viral genome shared 89.1 per cent nucleotide similarity with severe acute respiratory syndrome (SARS)-like coronaviruses from bats.
Another study, published in Nature, carried out the identification and characterisation of the coronavirus associated with the recent outbreak, revealed similarities with SARS coronaviruses.
The analysis uncovers evidence that the coronavirus has an origin in bats, although the animal source of this outbreak has not been confirmed.
Coronaviruses have been a source of infectious disease epidemics in humans, such as SARS and Middle East respiratory syndrome (MERS).
SARS-related coronaviruses are mainly found in mammals such as bats and are a potential threat to public health.
As of December 2019, an outbreak of respiratory illness has been reported, originating in a seafood market in Wuhan. Symptoms include fever, shortness of breath and pneumonia.
Zheng-Li Shi and colleagues from Wuhan Institute of Virology in China analysed samples from seven patients with severe pneumonia, six of whom were identified as workers from the seafood market in Wuhan, where the cases were first reported in December.
Full-length genome sequences obtained from five of these patients are found to be almost (over 99.9 per cent) identical to each other, and share 79.5 per cent sequence identity with SARS coronaviruses.
The researchers also found that the virus sequence was 96 per cent identical at the whole-genome level to a bat coronavirus, suggesting that bats are a probable source of this coronavirus.
The identification and sequencing of seven non-structural proteins also found in SARS coronaviruses demonstrates that this virus is a SARS-related coronavirus, which the authors provisionally name novel coronavirus 2019 (2019-nCoV), they said.
The resaerchers determined that 2019-nCoV enters cells through the same route as SARS coronaviruses, via the ACE2 cell receptor.
Antibodies isolated from patients infected with 2019-nCoV are shown to have the potential to neutralise the virus.
A previously identified horse antibody against SARS-CoV also neutralizes the virus at a low serum dilution, but whether or not anti-SARS-CoV antibodies cross-react with 2019-nCoV needs to be confirmed using serum from humans who have convalesced from SARS-CoV infection.
The researchers developed a test that can differentiate 2019-nCoV from all other human coronaviruses.
They showed that 2019-nCoV was detected in initial oral swab samples, but that subsequent samples (taken around 10 days later) did not have a positive viral result.
This finding suggest that the most likely route of transmission is through the airways of individuals, although the researchers note that other possible routes may be possible, and more patient data is needed to investigate the transmission routes further.
How do bats live with so many viruses?
Dr Peter Daszak, president of EcoHealth Alliance, who has been working in China for 15 years studying diseases that jump from animals to people, said, "We don't know the source yet, but there's pretty strong evidence that this is a bat origin coronavirus." He said, "It's probably going to be the Chinese horseshoe bat," a common species that weighs up to an ounce.
If he's right, this strain will join many other viruses that bats carry. SARS and MERS epidemics were caused by bat coronaviruses, as was a highly destructive viral epidemic in pigs.
One bat can host many different viruses without getting sick. They are the natural reservoir for the Marburg virus, and Nipah and Hendra viruses, which have caused human disease and outbreaks in Africa, Malaysia, Bangladesh and Australia. They are thought to be the natural reservoir for the Ebola virus. They also carry the rabies virus, but in that case the bats are affected by the disease.
Their tolerance of viruses, which surpasses that of other mammals, is one of their many distinctive qualities. They are the only flying mammals, they devour disease-carrying insects by the ton, and they are essential in the pollination of many fruits, like bananas, avocados and mangoes.
They are also an incredibly diverse group, making up about a quarter of all mammalian species.
But their ability to coexist with viruses that can spill over to other animals, in particular humans, can have devastating consequences when we eat them, trade them in livestock markets and invade their territory.
In a 2018 paper in Cell Host and Microbe, scientists in China and Singapore reported their investigation of how bats handle something called DNA sensing. The energy demands of flight are so great that cells in the body break down and release bits of DNA that are then floating around where they shouldn't be.
Mammals, including bats, have ways to identify and respond to such bits of DNA, which might indicate an invasion of a disease-causing organism. But in bats, they found, evolution has weakened that system, which would normally cause inflammation as it fought the viruses.
Bats have lost some genes involved in that response, which makes sense because the inflammation itself can be very damaging to the body. They have a weakened response but it is still there. Thus, the researchers write, this weakened response may allow them to maintain a "balanced state of 'effective response' but not 'over response' against viruses."
How to manage and contain the current outbreak of the virus officially known as 2019-nCoV, is, of course, of paramount importance now. But tracing its origin and taking action to combat further outbreaks may depend partly on knowledge and monitoring of bats.
"The outbreak can be contained and controlled," Dr Daszak said. "But if we don't know the origin in the long term then this virus can continue to spill over."
Scientists in China were already studying the bats carefully, well aware that an outbreak like the current one would most likely happen.
Last spring, in an article on bat coronaviruses, or CoVs, a group of Chinese researchers wrote that "it is generally believed that batborne CoVs will re-emerge to cause the next disease outbreak." They added, "In this regard, China is a likely hot spot." This wasn't clairvoyance, but conventional wisdom.
Certainly, rodents, primates and birds also carry diseases that can jump and have jumped to people; bats are far from alone in that regard. But there are reasons they have been implicated in several disease outbreaks and are likely to be implicated in more.
They are numerous and widespread. While bats account for a quarter of mammalian species, rodents are 50 percent, and then there's the rest of us. Bats live on every continent except Antarctica, in proximity to humans and farms. The ability to fly makes them wide-ranging, which helps in spreading viruses, and their feces can spread disease.
People in many parts of the world eat bats, and sell them in live animal markets, which was the source of SARS, and possibly the latest coronavirus outbreak that began in Wuhan. They also often live in huge colonies in caves, where crowded conditions are ideal for passing viruses to one another.