Why exactly does the coronavirus spread so easily among people?

When the first case of the new coronavirus was identified in December 2019, scientists found it to be very similar to the virus that caused the SARS outbreak in 2003.

Almost four months later, the number of Covid-19 virus cases is surpassing that of SARS. And while a majority of Covid-19 virus cases are mild and treatable, the sheer number of cases is causing concern. Scientists are asking: “Why is this virus spreading so fast?”

Now, experts have identified a couple of genetic and structural characteristics that might explain why this coronavirus is infecting humans so easily.

“Understanding transmission of the virus is key to its containment and future prevention,” stated David Veesler, a structural virologist at the University of Washington in Seattle, who posted his team’s findings about the virus protein on the biomedical preprint server bioRxiv on 20 February.

How does the coronavirus infect human cells?

The name “coronavirus” comes from the Latin word “corona”, meaning "crown", which refers to the crown-like spikes that can be seen around the virus under a microscope.

The spikes that are a key component of all coronavirus strains are significant as they attach the virus firmly to a cell membrane in your body.

But what makes this new coronavirus different from previous strains is the fact that the protein in the spikes differs from previous strains. The protein has a site which is activated by an enzyme called furin, which is present in our human cells.

Furin can be found in many of our human tissues, including the lungs, liver and small intestines. This is significant, because this means that the virus can latch on and activate in multiple organs, according to Li Hua, a structural biologist at Huazhong University of Science and Technology in Wuhan, China.

That is the reason why some of the symptoms in more serious cases also include liver failure, for example. SARS and the other coronaviruses didn’t cause the activation of furin.

This furin activation also enables the virus to spread more efficiently between humans.

Outcome not yet clear

According to an article published in Nature, researchers are still cautious about overstating the role of the activation site as a main reason why the coronavirus is spreading so rapidly and easily.

“We don’t know if this is going to be a big deal or not,” says Jason McLellan, a structural biologist at the University of Texas at Austin.

Some experts also reckon that they shouldn’t jump the gun by comparing furin activation to previous flu outbreaks. The deadly flu pandemic of 1918 didn’t involve furin activation, according to Lijun Rong, a virologist at the University of Illinois, Chicago.

Could this help us find a suitable drug?

According to the report, Li’s team are looking at molecules that could block furin as a possible way of preventing coronavirus.

Mclellan’s research group in Texas also found that the spike proteins bind successfully to a receptor on human cells called angiotensin-converting enzyme 2 (ACE2).

This receptor could also potentially be involved in a vaccine or treatment – anything that can block the ACE2 receptor could potentially make it harder for the coronavirus to enter cells.

Finding ways to prevent spreading

While scientists are doing their utmost, finding a targeted vaccine or treatment takes time. In the meantime, protect yourself by:

  • Washing your hands properly
  • Practising caution when travelling abroad
  • Keeping your own immune system strong
  • Being mindful of those who are immunocompromised and already ill
  • Coughing or sneezing into the crook of your arm.

READ | This week in coronavirus – what science is currently saying

WATCH | 6 handwashing mistakes that help coronavirus spread

READ | How an Ebola drug might fight Covid-19 virus

Image credit: Getty

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