Best and Worst: How Will the Outbreak Develop?

Since the outbreak of the deadly new coronavirus in Wuhan in December 2019, scientists and official health agencies around the world have been scrambling to contain its spread. The new coronavirus causes respiratory diseases and has infected tens of thousands of people. On January 30th the World Health Organization declared the outbreak a “public health emergency of international concern”, meaning it posed a threat to many countries and regions and required a coordinated international response.

Best and Worst: How Will the Outbreak Develop?

While the key details and mode of transmission of the new virus remain unknown, experts are predicting the best and worst scenarios that might emerge based on previous epidemiological cases and known information.

How many people will the new coronavirus infect?

The Chinese government has blocked the central city of the outbreak, and researchers are sharing data with the World Health Organization and their peers. Despite this, the number of confirmed cases continues to grow, with more than 9,000 cases accumulated the day before, mostly in China. According to a previous projection, the virus could infect 39,000 of Wuhan’s 30 million people (one of the model’s predictorscenarios, non-Wuhan actual population). “It looks like the virus is spreading in China, spreading too wide and too fast to really get it under control,” said Ian Mackay, a virologist at the University of Queensland in Australia. “

In the best case scenario, the number of people infected will decline as prevention and control measures take effect, says Ben Cowling, an epidemiologist at the University of Hong Kong. However, it is too early to say whether the practice of isolation and the heavy use of masks will be effective. He said the virus has an incubation period of up to 14 days, longer than most existing prevention and control measures.

According to another forecast model 1, the worst-case scenario would be that about 190,000 people could be infected in Wuhan. Scientists are particularly concerned about new outbreaks outside China. The virus has spread locally in Vietnam, Japan, Germany and the United States, but officials quickly quarantined infected people. As of January 30, no more than 100 cases had been reported outside China.

Is the new coronavirus difficult to eliminate?

If a virus can continue to spread in a group, it can be called a endemic epidemic. Chickenpox and influenza are endemic in many countries, but vaccination and home isolation of infected people can help control the outbreak.

A major question is whether the new coronavirus is stubborn and difficult to eliminate. If prevention and control measures fail, it has a good chance of developing a local epidemic. Like the flu, this could mean that as the virus spreads, deaths occur every year until a vaccine is available. If the virus can be transmitted through asymptomatic infected people, it will be more difficult to contain it, which increases the likelihood that the virus will develop into a endemic epidemic.

There have been several cases of asymptomatic infections, but it is not clear whether such asymptomatic or mild cases are widespread, and whether the condition is contagious and infectious. “The virus we are dealing with now may persist, or will persist forever. Mackay said.

The appearance of asymptomatic cases makes the new coronavirus different from its kinship and causes SARS coronavirus. In 2002-2003, the SARS virus broke out worldwide. However, the SARS virus usually spreads when an infected person has severe symptoms and needs to be hospitalized. Once the outbreak in the hospital is under control, SARS can be brought under control. There is no evidence that the SARS virus is still circulating in humans, Mackay said.

If prevention and control measures are effective, the rate of transmission will slow down, and each infected person will not infect more than one person, and the current outbreak will gradually disappear, Cowling said.

Will the new coronavirus mutate?

Some researchers worry that the new coronavirus mutates as it continues to spread, leading to faster transmission or making younger groups more susceptible to infection. So far, the virus has led to serious illness and death, but is concentrated in the elderly, especially those with underlying diseases such as diabetes and heart disease. The youngest death reported to date is a 36-year-old Wuhan male with no known underlying disease.

Kristian Andersen, an infectious disease researcher at the Scripps Research Institute in California, isn’t too worried about the new coronavirus’s virulence. Viruses are constantly mutated as part of their life cycle, he said, but these mutations generally do not increase the virus’s virulence and do not cause more serious diseases. “In my mind, there are no exceptions to the outbreak of pathogens,” he said. “

Andersen says that when the virus runs from one animal host to another (and possibly the way the new coronavirus first infects humans), there is a pressure to choose between the virus and the survival of the new host. But even if any, there is little effect on human disease or the spread of the virus. He added that most of the mutations are not conducive to or have no effect on the virus. A 2018 study analyzed SARS virus 2 in primate cells and found that a virus mutation that had been present during the 2003 outbreak may have made the virus less virulent.

MacKay said researchers have publicly shared dozens of genetic sequences of the new coronavirus strain, and that as the outbreak progresses, the continuous release of sequence information will reveal genetic changes in the virus. “Unless the sequence of viruses changes, their behavior will not change, which requires us to observe the virus’s constant changes. He said.

How the mortality rate of the new coronavirus will change

The fatality rate of one virus, the rate of death among infected people, is difficult to count in the development of the outbreak, as new cases and deaths are constantly being updated. So far (30 January), of the nearly 10,000 cases of new coronavirus infection, 213 have died, or 2%-3% of the mortality rate; Mark Harris, a virologist at the University of Leeds in the UK, told Science Media Centre in London that the known mortality rate of the new coronavirus could fall as more cases of mild and asymptomatic illness are diagnosed.

There is currently no effective drug against the virus. It is believed that two anti-HIV drugs can target a protein that helps the coronavirus replicate, and is currently being treated for an effect. Scientists have also found other existing drugs that target this function, and several international research organizations are developing targeted vaccines.

The mortality rate also depends on how China’s health system responds to the large number of confirmed cases. Dots and take a ventilator to ensure that their immune system gets enough fluid and oxygen to fight the virus. China is stepping up construction of two hospitals in Wuhan to treat infected patients. But once the virus spreads to resource-poor parts of the world, such as low-income countries in Africa, their health systems may struggle to cope, says Sanjaya Senanayake, an infectious disease expert at the Australian National University.

Who Director-General Tan Desai, declaring the Wuhan outbreak a global health emergency, said he was most concerned that it would spread to other countries and regions where health systems are fragile.

If the new coronavirus spreads around the world, the death toll could increase significantly. The current fatality rate is 2 to 3 per cent, which is not as high as SARS, but also high for infectious diseases, says Adam Kamradt-Scott, a global health and safety expert at the University of Sydney. The 1918 pandemic, also known as the Spanish pandemic, infected about 500 million people, a third of the world’s population at the time, and more than 2.5 percent of the infected population died – an estimated 50 million people.

Kamradt-Scott believes that the new coronavirus outbreak in China should not be serious because it is not infected and killed mainly by healthy young people.