Researchers are rushing to learn more about the epidemiology and genetic sequence of the coronavirus, which is rapidly spreading in Asia and beyond. At the same time, people do not have effective drugs for the treatment of coronavirus infections, just as there are no certified vaccines to prevent them.
Health authorities around the world are concerned about an outbreak of a mysterious virus that emerged last month in the Chinese city of Wuhan. Local officials have confirmed more than 500 cases of infection causing respiratory illness and 17 deaths. Several cases have been reported in other parts of Asia and one in the United States.
Researchers are rushing to study the virus in more detail to see if it could trigger an outbreak similar to the Severe Acute Respiratory Syndrome (SARS) epidemic that hit southern China in 2002-03 and killed 774 people in 37 countries. Both viruses belong to the vast family of coronaviruses, which includes the common cold.
Understanding the nature of the outbreak is especially important because massive travel from Friday to Chinese New Year threatens to accelerate the further spread of the virus.
How is the virus spread?
The most pressing question is how the virus spreads. Chinese authorities have confirmed that some of the cases are caused by person-to-person transmission, but whether this occurs on a regular basis is still unclear.
“It’s important to understand if the rate and efficiency of the spread is at the level of the epidemic,” says Neil Ferguson, a mathematical epidemiologist at Imperial College London. Monitoring the incidence of new cases and the onset of symptoms on a case-by-case basis will tell scientists how easily the virus spreads from person to person and whether the outbreak has the potential to continue.
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How lethal is it?
At first, scientists sounded the alarm about the lethality of the Wuhan virus, because among the first infected there were many cases of severe pneumonia. But the appearance of milder cases dispelled some of the fears. With 17 deaths in more than 500 cases, the virus does not appear to be as deadly as SARS, which killed approximately 11% of those infected. But it is "too early" for optimistic assessments, Ferguson said.
Where did he come from?
Authorities are developing a theory that the virus originated in an unknown animal and then spread to humans in a large Wuhan animal and seafood market. Identifying the animal source of the virus will help bring the current outbreak under control and properly assess its threat, according to the researchers - and at the same time prevent similar epidemics in the future. Genetic sequencing suggests that the Wuhan virus is linked to coronaviruses carried by bats - including SARS and its close relatives. However, other mammals also carry these viruses, and it is likely that SARS was transmitted to humans from the animal civet (aka civet).
In the now closed market - where the outbreak appears to have started - wild animals were also sold. According to Ben Cowling, an epidemiologist at the University of Hong Kong, tracing similar cases on the market, as well as analyzing animals from the market and their containers and cells for infected genetic material, will help determine the source.
What do we know from the genetic sequence of the virus?
Genetic sequencing of the Wuhan coronavirus provides insight into its origin and distribution. Laboratories in China and Thailand have sequenced the genomes of at least 19 strains found in infected people and made them publicly available. “This is an outstanding case considering it has been only two weeks since the start of the work,” says Trevor Bedford, an evolutionary geneticist at the Cancer Research Center. Fred Hutchinson in Seattle, Washington. It analyzes the sequences as they come in. “They are doing a great job and have a very fast communication,” he adds.
Stop the Wuhan virus
Bedford says the most striking thing about the sequences is how similar they are to each other. “There is very little variety. I expected more and, I think, others too. The lack of genetic diversity suggests that the common ancestor of various human strains appeared in November or December and quickly spread without much time to mutate. The acquired mutations are different for each virus sequence. However, Bedford adds, it is not yet possible to conclude from the genome whether it has spread rapidly among humans or in the animal kingdom. A similar conclusion was reached by evolutionary geneticist Andrew Rambaut of the University of Edinburgh in the UK, who published his analysis on January 20.
Bedford says the new viral sequences will help conclude whether most cases are due to re-spread of the virus from animals to humans with limited human-to-human transmission, or whether the virus initially spread to a small number of people, and most of the current cases are due to secondary human-to-human transmission. “I think this will be the main goal of epidemiologists around the world,” he says. The genetic data of the animals from which the virus was transmitted to humans will help determine the degree of transmission, Bedford concludes.
How fast is the Wuhan virus spreading?
Also, he says, such sequences will help determine the genetic changes that caused the virus to spread from animals to humans. And if the outbreak drags on due to extensive human transmission, Bedford and other geneticists will look for signs of further mutations that make the virus more efficient in spreading among humans.
At the same time, Bedford warns that these conclusions are purely preliminary, because there is not enough data. “The situation will change significantly if a number of core samples are added,” he says.
Is there a cure for coronavirus?
It has been proven that there are no effective drugs for the treatment of SARS or other coronavirus infections in humans, and there are no certified vaccines to prevent them.
A team of employees at the China National Research Center for New Drugs Research in Beijing is developing treatments by blocking receptors on human cells through which infection occurs. A sequence comparison between SARS and the new Chinese viruses published on January 16 showed that they bind to the same receptor. The team expects to resume work on treatments for SARS and adapt them to counter the latest virus.
Ewen Callaway, David Cyranoski