The existence of coronavirus has long been known. As a virus that can infect the respiratory and digestive tracts of animals and humans, it has not received enough attention from humans for a long time. This arrogance is also excusable - in healthy people with normal immunity, coronaviruses cause only very mild symptoms. However, during the first decade of the 21st century, SARS broke out. In July 2003, data showed that the SARS virus caused 8096 cases of infection and 774 people death in 27 countries. 10 years later, the Middle East Respiratory Syndrome caused by the MERS virus brought 1,728 confirmed cases in 27 countries and claimed 624 lives.
In 2018, a Nature Reviews Microbiology review paper pointed out that according to their genome and structure, coronaviruses can be divided into 4 major categories, of which α and β only infected mammals, and γ and δ mainly infected birds. The well-known SARS and MERS viruses belong to the β coronavirus.
The infection of these viruses by humans is inseparable from the participation of other animals. Scientists found early strains of SARS in civet. Many people in close contact with civets have also become infected with SARS. Subsequent further research found that the civet is only an "intermediate host", and the source of the virus may be bats.
The MERS virus is relatively more complicated. Although scientists also believe that the viruses originally came from bats, there are indications that camels have become a "repository" for such viruses. This can explain why in the Middle East, where humans and camels have more contact, there have been cases of human infection with the MERS virus. On the contrary, for SARS, because humans have little direct contact with bats, they are in the middle of being infected. After the host became extinct, no new cases of SARS were observed.
The pathology of SARS and MERS coronaviruses is very similar. Both rely on the glycoproteins on the surface of the virus to bind to receptors on the surface of the cell, and release RNA in the cytoplasm to guide the synthesis of new virus particles. The difference is that the SARS virus recognizes the ACE2 receptor, while the MERS virus recognizes the DPP4 receptor. Besides these viruses have a variety of strategies to "immune escape" to prevent the innate immune system from responding to them.
We currently lack relatively effective antiviral therapies for SARS and MERS, so we can only provide some complementary treatments. Also in a review published in 2016, the authors noted that most of these patients received treatment with ribavirin and various interferons, and sometimes also received broad-spectrum antibiotics and oxygen. In the treatment of SARS, it is also advantageous for the combination of bavirin and corticosteroids. In addition, lopinavir and ritonavir, which are used to treat HIV infection, are also used in some patients with coronavirus infection. Finally, the authors point out that sera and antibodies from patients in rehabilitation may help.
"Unexplained pneumonia" has occurred in Wuhan, China since December 2019, and the number of cases has continued to rise. The virus is a new type of coronavirus that can be infected by humans and is highly worrying because of its association with SARS. Chinese authorities, WHO and other governments are working to control the spread of the virus. The source of the new type of coronavirus has not been found, the route of transmission of the epidemic has not been fully grasped, and the mutation of the virus still needs to be closely monitored.
References
- Cui, J., et al. Origin and evolution of pathogenic coronaviruses. Nat Rev Microbiol 17, 181–192 (2019)
- de Wit, E., et al. SARS and MERS: recent insights into emerging coronaviruses. Nat Rev Microbiol 14, 523–534 (2016)