Why did Coronavirus Spread so Fast?
During the Coronavirus outbreak, the total number of infected patients has exceeded 1,190,000.
Despite the efforts of a growing number of countries to detect, treat, and contain the virus, the growth rate of infected cases still remains high.
Last week, the US had an exponential growth with more than 20,000 new cases each day. Although most of the cases are in New York City, Andrew Cuomo, the governor of New York, warned that what was happening in New York is very likely to happen in other parts of the country in the coming weeks.
If Cuomo is right, the number of infected cases will at least double. Why is the Coronavirus spreading so fast? What makes it so infectious?
The reproduction number (the “R0”) is an important property of infectious diseases. It denotes the expected number of infections that one case can make. Joacim Rocklöv, who is a Professor of Sustainable Health at the Umeå University in Sweden, estimates the reproduction number ranged from 1.4 to 6.49 in twelve studies of the corona virus epidemic in China and had an average of 3.28.
If we compare the Coronavirus with SARS, which has an R0 value of 2.8, coronavirus is significantly more infective.
A handful of genetic analyses have identified that the reason why COVID-19 can infect humans so readily is because of a protein on its surface that is referred to as a ‘spike’. To infect a cell, coronaviruses use the ‘spike’ protein that binds to the cell membrane, a process that's activated by specific cell enzymes.
Genomic analyses of the new coronavirus have revealed that its spike protein differs from those of close relatives and suggest that the protein has a site on it which is activated by a host-cell enzyme called furin. SARS and other coronaviruses in the same genus as the new virus do not have furin activation sites.
This is significant because most human tissues have furin.
Furin is found in the lungs, liver, small intestines and elsewhere in the human body, which indicates that COVID-19 is not only capable of causing breathing difficulties but also has the potential of attacking multiple organs.
During the Wuhan lockdown, a large number of patients were having pulmonary failure along with hepatic failure and kidney failure. There was a Coronavirus patient in Beijing with meningitis, which indicates that the virus can also attack the central nervous system as well. The furin activation sites allow the Coronavirus to spread much more readily than SARS, and has allowed the virus to infect more than ten times the number of people who contracted SARS.
Since the coronavirus infects the host cell by combining furin on the host cell with its own spike protein, then if we can block or eliminate this process, we can stop its infection. Lijun Rong, a virologist at the University of Illinois in Chicago, is looking at molecules that could block furin.
Researchers at multiple institutions, including Missouri’s Washington University in St. Louis, have started taking blood from survivors of the disease and using the antibodies they harvest to treat critically ill patients. This method will be unable to cure an individual of the disease, but it can alleviate the symptoms.
Unfortunately, no one knows when a medicine or vaccine for the virus will be produced. With all the efforts of our researchers, lab workers and medical workers, eventually the bad times will pass.
Written by Zhehao Zhang & Ethan Samuels & Edited by Alexander Fleiss