Why is the new coronavirus very 'insidious'?

It is important to note that the information provided in this Series is intended for your general knowledge only and is not a substitute for professional medical advice or treatment.

Coronaviruses are a family of viruses that exists widely in nature. It is usually transmitted in vertebrates such as mice, pigs, cats, dogs, birds and so on. Under certain conditions, coronaviruses can mutate and infect humans through intermediate hosts. The novel coronavirus, the seventh known coronavirus able to infect humans, is more infectious, more widespread, and more insidious than other coronaviruses. According to currently known information of the novel coronavirus, its wiliness mainly comes from the following six aspects:

First, its survival ability is strong. The novel coronavirus can adapt to a variety of different environments. Normally, it can survive for 48 hours at room temperature, but in suitable environment (such as when temperature is 20 degrees Celsius and relative humidity is 40-50%), it can survive for up to 5 days.

Second, its incubation period is long. The incubation period of novel coronavirus pneumonia is usually 1-14 days, mostly 3-7 days. Studies have shown that the median incubation period is 4 days, while the longest incubation period can last up to 24 days. Cases with incubation period of 28 days even appeared in Guangzhou. This means that the normal isolation cycle could not completely guarantee that the quarantined people are not infected, which may lead to patients being omitted.

Third, its source of infection is concealed. There are asymptomatic infectious patients of novel coronavirus pneumonia. The study showed that the proportion of asymptomatic infections is 1.2%. This means that conventional measures to prevent and control infectious disease, such as temperature measurement, are not effective in identifying patients and can only be used to confirm cases through testing reagents, which may lead to a large number of potential infections mixed with healthy people.

Fourth, there are various ways of transmission. Respiratory droplets and close contact transmission are the main modes of transmission. It can also be transmitted through mucosa membrane, with the possibility of aerosol transmission in closed environment and aerosol or contact transmission caused by fecal and urine pollution to the environment. This means that all groups of people may become infected in the case of inadequate protective measures.

Fifth, its infection is widespread across population. As the novel coronavirus pneumonia is generally susceptible, anyone may become a potential virus carrier, so it is difficult to take targeted local prevention and control measures customized for its susceptible population, which increases the difficulty of prevention and control.

Sixth, its clinical symptoms are easily confused with other diseases. The early symptoms of novel coronavirus pneumonia are not obvious and similar to common seasonal infectious diseases such as influenza, leading patients to be omitted and misdiagnosed. However, in the late stage of novel coronavirus pneumonia, the disease develops very fast, and once it is converted to severe cases, it is extremely difficult to treat.