By Jessica Hamzelou
At the end of 2019, health authorities in China alerted the world of a potentially new virus that had caused pneumonia in a handful of people in Wuhan since mid-December. Since then, the number of cases has exploded, and over 600 cases are now confirmed. The virus has since been confirmed to be a new coronavirus, in the same family as SARS and MERS.
What is a coronavirus?
Coronaviruses are common, and typically cause mild respiratory symptoms in people, such as a cough or runny nose. Some are more dangerous. SARS, which infected over 8000 people, was responsible for 774 deaths during an outbreak that began in 2003. MERS, which was first identified in 2012, is even more deadly around 34 per cent of people infected with the virus die.
What are the symptoms of the new virus?
People who have been diagnosed with the virus tend to have a fever and cough, and some have difficulty breathing. The symptoms appear to set in between two days and two weeks after the person has been exposed to the virus, according to health authorities.
How is it diagnosed and treated?
Health authorities in China have sequenced the genome of the virus, and have shared this information, allowing groups around the world to be able to test for the virus. There are no specific antiviral treatments for the infection, so people with the virus are treated for their symptoms.
Where did the virus come from?
The World Health Organization told journalists this week that the agency is still working to pin down the source of the virus. But many of the first confirmed cases were in people who had visited a food market in Wuhan. The market, which sells live farmed and wild animals, has since been closed and disinfected.
A recent genetic analysis suggests that the virus resembles similar viruses that infect bats and snakes. Researchers believe that the virus may have resulted from separate viruses in bats and snakes recombining. This could have happened in the wild, but may also have occurred in the market, where the animals have been kept in close proximity to each other.
How did the virus spread to humans?
The same genetic analysis suggests that the virus may have developed the ability to jump from snakes to people thanks to a mutation in a gene for a protein. If the virus was secreted in the animals feces, this could have become aerosolised and breathed in, some researchers speculate.
Where has the virus spread to so far?
Most of the confirmed cases have been in Wuhan, where at least 444 people are known to have been diagnosed with the virus. But many more cases have been confirmed in China, including in Beijing, Shanghai and Guangdong. In total, there are over 600 confirmed cases in China alone.
But the virus has also spread internationally. Cases have been confirmed in Thailand, Japan, South Korea, the US, and most recently Singapore and Vietnam. So far, all the confirmed cases are people who have travelled from China. But hundreds of suspected cases are being investigated in countries across Asia, as well as the UK and Mexico.
How contagious is the virus?
It is too soon to know how easily the virus will spread. The virus is airborne, and we know it can be transmitted between people. Chinese authorities have presented evidence of fourth-generation cases in Wuhan, and second-generation infections outside of the city.
Yesterday, the World Health Organization heard preliminary calculations for the average number of infections that each infected person may go on to cause, known as R0. This is estimated to be 1.4 to 2.5 people per infected person. In comparison, seasonal flu usually has an R0 of around 1.3.
How deadly is it?
So far, 17 deaths have been linked to the virus, which suggests a low fatality rate of around 4 per cent. Most people feel this is somewhere on a spectrum between a relatively mild infection and SARS, which had a very high case fatality rate, says Mark Woolhouse at the University of Edinburgh, UK. Again, it is too soon to be sure. There are concerns that the virus could mutate and become more dangerous.
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