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Li Haichao: My thoughts on COVID-19 and the prevention measures

Peking University, March 25, 2020: In the face of the global outbreak of COVID-19, Peking University Alumni Association invites Li Haichao to share with us his thoughts on COVID-19 and relevant prevention measures. Li, who comes from the Division of Respiratory and Critical Care Medicine, Peking University First Hospital, is also a member of the national emergency medical rescue team from Peking University to Wuhan, Hubei. 


Li Haichao

Key points

1. There are no specific antiviral drugs.
2. There is no need to worry about the long incubation period.
3. For patients who are fully in line with the discharge criteria, positive results of the nucleic acid retest do not necessarily mean recurrence.
4. The discharged patients should quarantine themselves at home for 14 days.
5. Airborne transmission requires specific conditions (confined space, prolonged contact), so there is no need to upgrade protection and disinfection measures.
6. More important measures are to wear surgical masks in public spaces, and pay attention to hand hygiene.

Possible antiviral drugs

It can be said that there are no definitely effective antiviral drugs at present. As for the effectiveness of the drugs under clinical trials, we must wait for the results. Therefore, for COVID-19 patients, especially for the mild cases, the use of a variety of antiviral drugs is not effective, and may lead to several side effects. Most mild patients can heal by themselves and only need symptomatic treatment.

The long incubation period

Currently, the recognized incubation period is between 1 to 14 days, most commonly between 3 to 7 days. Now all the quarantine requirements are set in accordance with this knowledge. How about the report saying that the incubation period is as long as more than 20 days? In my opinion: First, these are extremely rare cases. Journalists are not epidemiologists, so they might not be able to get a clear picture of possible contacts (of course, epidemiological investigations may not be clear, either, especially when deliberate concealment of information occurs). Therefore, the actual incubation period of these cases is doubtful. Second, even if the incubation period lasts that long, it remains a small probability event. Its impact is also very limited, the worst of which may be point-spreaders. There is no case of super-spreaders with a long incubation period. To conclude, the incubation period may be long, which requires attention. In general, however, the impact is basically negligible. There is no need to panic.

The positive results of the nucleic acid retest after discharge

For a COVID-19 patient, discharge should be approved once symptoms are significantly improved after treatment and the chest CT shows obvious shadow absorption, or the remaining fibrous cord shadow (some will be absorbed later) shows convalescent changes, and two nucleic acid tests are negative. Now another criterion has been added that the antibody test should be positive. The fact that a discharged patient is tested positive for nucleic acid again does not mean recurrence!!! The recovery period of some patients is relatively long, because their lung function has not fully recovered. They may easily feel tired, and will be short of breath after exercises. As long as their condition continues to improve, it will be fine!

Positive results of the nucleic acid retest suggest that a discharged patient may still carry the virus, but it is also possible for the virus to be expelled. The epidemiological significance of this situation needs further research. For this situation, some current measures demonstrate preventive effects, such as a prolonged quarantine period of 14 days after discharge. With the passage of time, the possibility of the test result turning negative will be further increased.

Will there be a continuous spreader like "Typhoid Mary" (a famous case in the history of infectious diseases)? The estimation is highly unlikely. The infectious significance of these "poisonous" people remains to be seen, because a case with a positive nucleic acid test result is not necessarily infectious. At present, we employ very sensitive qualitative measurement, not quantitative measurement, but the effect of virus transmission is closely related to the number of the virus. If the test is positive, while the virus number is very small, it is basically non-significant. Therefore, the significance of positive retests remains to be determined. More researches are needed in the future to decide whether discharged patients are required a 14-day quarantine. In summary, for convalescent patients who are retested positive: first, do not worry about recurrence. Be patient and wait for recovery. Second, follow the 14-day quarantine protocol after discharge.


Since the commonest routes of transmission are droplet transmission and contact transmission, it is very important in public places (and places where patients are diagnosed) to wear medical surgical masks, wash hands frequently, and avoid touching things, especially the face. There is no need to wear an N95 mask, which is needed by the medical staff in the infection ward. Airborne transmission is a small probability event, which is also the case for the news that the presence of virus in urine and stool may cause aerosol transmission. Transmission is possible on the condition of a prolonged stay in a confined space with high virus content. Therefore, as long as we pay attention to ventilation and keep the distance between people, transmission will basically not happen.

Disinfection in public space

My feeling is that disinfection measures have gone too far now. Spraying disinfectant on the ground is of little significance. Even if there is virus on the ground, it will only survive for a few hours. During the time, firstly, it cannot fly (as it falls to the ground with droplets). Secondly, even if it flies, it cannot accumulate the number needed for airborne transmission, hence no threat. So there is no need to spray massive disinfectant in well-ventilated areas. Because droplets may stick to clothes, there could be a large number of the virus on the clothes. But the virus will die soon, so there should be no problem as long as the clothes are hung overnight. It is unnecessary to keep washing clothes. As for other surface disinfection, attention should only be paid to areas where patients definitely stay or touch. Proper disinfection is enough. 

Hand hygiene facilities

The most, most important thing is to pay attention to hand hygiene. I do not advocate touching doorknobs or elevator buttons with paper towels, which is a huge waste, as well as an unnecessary measure. If you have touched a suspicious or uncertain surface, it is of vital importance to wash your hands after you go back to your home or the office area. Hand-washing is enough. Hand disinfectant is also recommended.


Translated by: Huang Rong (School of Health Humanities, Peking University)
Source: Peking University Alumni Association