On December 31, 2019, China informed the World Health Organ-ization that a new coronavirus
was infecting people in Wuhan city (population 11 million), the capital of Hubei Province. The first case had been identified on December 8. Till date, the new virus has infected at least 8,000 people, caused at least 156 deaths and spread to multiple countries.
This is despite desperate attempts to quarantine Wuhan and other Chinese cities. The disease has arrived in India, courtesy a native of Kerala who was a student at Wuhan University. An estimated 40 million people are in a “no-travel” zone in China. Many commercial flights into China have been cancelled. The UK is insisting on two weeks quarantine for any traveller out of China, India has also imposed quarantine.
This is a zoonotic coronaviruses, a virus which can mutate to be transmitted from animals and birds to human beings. For example, SARS, which also started in China is believed to have leapt species from bats and civet cats, to humans. It is assumed the Wuhan virus (now called the Novel Coronavirus
or NCoV) also leapt from an animal or bird to a human host and human-to-human transmissions are now occurring.
While the disease has flu-like symptoms, there may be a period of several days, when an infected person could display no symptoms. The spread of infectious diseases depends on many factors. One is, ironically, good infrastructure. In the 21st century, infectious cases can travel across the planet in a few hours. China with its excellent infrastructure can therefore, “export” a disease more easily than say, West Africa. We’ve already seen this with SARS in 2003.
Medical statisticians judge how infectious a disease is, by calculating a Basic Reprodu-ction Number (R0 or R-nought in the jargon). This R0 indicates the average number of people, one infected person may infect before he or she is cured (or dies). The higher the R0, the more infectious the disease.
If the R0 is less than 1, the disease is self-limiting. It will gradually die out. If the number is higher than 1, the disease will spread unless patients are isolated. This R0 number can vary widely. Influenza for example, has a R0 of 2-3, while measles has an R0 of 12-18. This means that a single measles case could lead to 18 more infections. A highly infectious virus (like the common cold) could be non-fatal, and therefore, not so scary. But an infectious disease, with a high fatality rate like say, Ebola, is really frightening.
As of now, there isn’t enough data to judge either the R0, or the fatality rate of NCoV with much accuracy. But researchers are making preliminary estimates. Two papers with multiple authors have been released (neither is peer-reviewed yet).
One of these, from a team of Hong Kong academics
says “We estimated that the mean R0 ranges from 2.24 (95 per cent CI: 1.96-2.55) to 3.58 (95 per cent CI: 2.89-4.39) associated with 8-fold to 2-fold increase in the reporting rate.” Even the lower estimate of 2.2 implies the disease is likely to spread rapidly.
The other paper
, authored by a team from the Guangdong Provincial Center for Disease Control and Prevention says, “The average incubation duration of 2019-nCoV infection was 4.8 days. The average period from onset of symptoms to isolation of 2019-nCoV and SARS cases were 2.9 and 4.2 days, respectively.” It continues “The 2019-nCoV may have a higher pandemic risk than SARS. The implemented public-health efforts have significantly decreased the pandemic risk. However, more rigorous control and prevention strategies and measures are needed to contain its further spread.”
Chinese scientists have done a pretty good job of getting data to the global scientific community. By January 10, China had sequenced and released the NCoV genome
. This allows patients with flu-like symptoms to rapidly tested and diagnosed.
Genome sequencing is the first step in trying to generate a vaccine. The genome has now been sequenced from multiple patients (including patients in Thailand). Genomes from later infections can be compared to early ones to judge mutations.
The rate of mutation can tell us how long the virus has been in the “wild”, and where it originated. The genome of the Wuhan virus is 29,903 bases long, and of very recent origin, because it has low mutations. Scientists estimate that it’s likely to have originated in bats, jumped to some animal commonly consumed in Wuhan, and then to humans. The human version is believed to have “first appeared no earlier than October 30, 2019, and no later than November 29”.
There have been terrific developments in genetic research in the last decade with new tools like CRISPR being discovered and deployed. How well-prepared is the world now to contain and hopefully, cure, a new disease? NCoV will be a test case.