2019-nCoV coronavirus may be more contagious than initially expected

Wuhan, China, continues to spread, infectious disease specialists are trying to learn more and more about the virus and its dynamics. The fact that the virus is transmitted long before the first symptoms appear already makes its control more complicated than its counterpart causing SARS. In addition, new estimates reveal that 2019-nCoV could be much more contagious than initially expected. Although these updated estimates are not yet fully confirmed, they could push the authorities to add to the measures already in place.

The coronavirus epidemic has reached at least 13 countries. As of Wednesday, January 29, there were more than 6,000 confirmed cases of the virus, while tens of thousands of people are under medical surveillance worldwide. According to the latest reports, more than 170 people have died from the virus.

2019-nCoV can spread before symptoms appear, which means that it is more difficult to limit transmission between people. There are confirmed cases of viruses in Asia, the United States, Australia and Europe.

So far, all cases outside of China appear to have been in people who have traveled from Hubei Province, where the epidemic began. Confirmed cases have been reported in mainland China, Hong Kong, Macao, Thailand, the United States, Australia, Japan, Malaysia, Singapore, Taiwan, France, Germany, South Korea , in Vietnam, in Canada, in Nepal. So far, all recorded deaths have occurred in Hubei Province.

A potentially more contagious coronavirus than initially expected

The scale of the epidemic will depend on the speed and ease of transmission of the virus between people. According to data collected until January 18, it appears that on average, each person infected with the virus transmits it to between 1.1 and 3.5 other people, according to an analysis by Natsuko Imai and his colleagues at Imperial College London. Using similar estimates, Robin Thompson of the University of Oxford predicts that there is a one in three chance that someone who brings the virus to the UK will spread it to other people in the country.

The original estimates of contagiousness of the virus defined a terminal of transmission located between 1.1 and 3.5 people. Credits: Natsuko Imai et al. 2020

This estimate is based on data collected since the start of the epidemic. Thompson hopes that as countries step up their efforts to control the spread of the virus, the chances of this happening will become less.

But there is still a lot we don't know about the virus, and some researchers suggest it could spread faster than expected. A study, based on data collected between January 10 and January 21, estimates that each person infected with the virus can transmit it to between 3.1 and 5.4 other people (compared to 1.1-3.5 previously estimated).

The new estimates define a transmission terminal located between 3 and 5 people. Credits: Shi Zhao et al. 2020

The work, by Shi Zhao at the University of Hong Kong and his colleagues suggests that the virus is much more contagious than originally thought. Thompson's estimate was calculated on the assumption that the virus is not contagious until symptoms appear - and this no longer appears to be the case. " If the virus is able to spread before symptoms appear, it could certainly explain why the virus spreads faster than SARS, " says Thompson.

2019-nCoV: a different epidemic from that of SARS 2003

Comparisons have been made between pneumonia caused by the new virus and SARS (severe acute respiratory syndrome), which infected more than 8,000 people during a global epidemic that started in 2003. The viruses belong to the same family and can both cause fever and pneumonia. So far, the new virus appears to have a lower death rate. Based on the number of reported cases and deaths, the rate appears to be around 2.8%, compared to 9.6% for SARS. But it is too early to know how dangerous the virus is.

We are still in the early days of the epidemic, says Thompson. The virus spreads faster than SARS. " It took several months for SARS to cause a thousand cases, " said Thompson. " It caused almost 3000 cases in three weeks ." The SARS epidemic ended in 2004 - no cases have been reported since. Health agencies have brought the virus under control by isolating infected people and screening passengers for air travel.

Such measures will be more difficult with a virus that can spread before symptoms appear. There is also always a risk that the virus will mutate to become more contagious or fatal. However, there is no evidence yet that the virus has mutated in humans, and the World Health Organization (WHO) has stated that the virus appears to be stable.

So how worried should we be? WHO is still reluctant to declare a public health emergency of international concern, although the organization says the risk of contracting the virus is "very high in China, high regionally and high globally".

Chinese provinces under quarantine and closed borders

Meanwhile, Chinese health officials have taken unprecedented steps to try to control the spread of the virus. Wuhan, where the epidemic began, has been quarantined - public transport has been closed, the airport is closed, and the use of personal motor vehicles has been banned. Immigration services to the city have been suspended. Several other cities have also been quarantined , affecting tens of millions of people.

Chinese authorities have also extended the Lunar New Year holidays. Holidays were due to end on January 30, but this has been extended until February 2, and schools and universities remain closed until further notice. More and more countries are filtering air travelers from China. Mongolia has closed its borders with China and the Malaysian government has declared that it will not issue visas to people in the affected regions.

Temporary ban on the sale of wildlife

The Chinese government has also temporarily banned the sale of wild animals at markets and restaurants. Although the origins of the virus are still unclear, it is believed to have been transmitted from bats to humans, possibly through snakes or mink. All of these animals are said to have been sold on the Huanan seafood market in Wuhan, where the first cases of the virus were reported.

The Wildlife Conservation Society (WCS) has requested that the ban be made permanent. " Poorly regulated live animal markets, mixed with illegal wildlife trade, offer a unique opportunity for viruses to spread from wild hosts to the human population, " Christof Walzer told WCS in a statement.


Preliminary estimation of the basic reproduction number of novel coronavirus (2019-nCoV) in China, from 2019 to 2020: A data-driven analysis in the early phase of the outbreak 

Shi Zhao, Jinjun Ran, Salihu S Musa, Guangpu Yang, Yijun Lou, Daozhou Gao, Lin Yang and Daihai He4,

Post a Comment

Previous Post Next Post