In 2003, during the SARS crisis, I was still living in the U.S. In March of that year, based on data on the occurrence of newly confirmed cases since the first SARS case was identified in Guangdong in December 2002, and taking into account the isolation and quarantine measures then in place, I predicted that the epidemic would end in June, which it actually did. How did I manage to do so?
The key is to focus on the number of newly confirmed cases. At the beginning, after the initial incubation period, the number of newly confirmed cases will undergo a very rapid and accelerating rise, then it will decelerate and finally reach a peak, and then it will begin to fall. If and when the number of newly confirmed cases drops to zero, the epidemic is under control. To achieve this goal, two essential measures must be undertaken. First, all the identified patients must be totally isolated and treated. This also prevents them from further infecting other people. Second, the potential transmission by the as yet unidentified infected patients must also be prevented. When transmission can be effectively stopped, all of the remaining unidentified patients will eventually be identified after the incubation period, and they can be appropriately isolated for treatment.
Once a new patient was identified and isolated, and with the medical personnel taking all proper precaution, he or she would no longer be able to transmit the virus. Only the as yet unidentified patients could continue to transmit the virus. But sooner or later, and certainly after the incubation period, all previously unidentified patients would become identified, and would be isolated. Of course, in the interim, these as yet unidentified patients could still infect others, but if everyone is vigilant and maintains proper precaution, the probability of transmission can be kept very low. If transmission of the virus can be limited, the total number of unidentified cases would decline over time, falling to zero eventually, and the epidemic would be over.
Preventing transmission by the unidentified patients is extremely important; otherwise, the number of new and as yet unidentified patients will continue to rise. The transmission of the SARs virus actually requires either direct or indirect physical contact, typically with exchange of body fluids, between an infected patient and a potential patient. Direct physical contacts, including hand-shaking, kissing, hugging, or simply touching, can all result in transmission. Indirect physical contact could also lead to transmission. For example, if an infected patient had touched an inanimate object such as a door knob or an elevator button, and the potential patient did the same afterwards, infection could occur. It could also happen if the infected patient handed a gift to a potential patient, without either one of them wearing gloves.
A critical parameter is the number of new patients that a SARS patient would be likely to infect before he or she was identified. Obviously, this depends on the length of time that a SARS patient could remain unidentified, the degree of caution exercised in the avoidance of direct and indirect physical contacts by others, as well as the natural infectiousness of the virus itself. Working from the newly identified patient data backwards, and assuming an incubation period, such numbers were estimated, which turned out to be quite low on average, on the order of low single digits, and declining over time. I could therefore predict when this number would fall to zero, which would signal the end of the SARS epidemic.
Controlling the current coronavirus epidemic requires a similar strategy. We need to identify all of the infected patients as soon as possible, and isolate and treat them, so that they can no longer transmit the virus. Moreover, once a new patient is identified, we can also identify other people with whom he or she has had direct or indirect physical contact, and pro-actively test these potential patients for possible infection, and isolate and treat them if necessary. The early identification of newly infected patients, perhaps even before they display symptoms, further reduces the probability of transmission and enhances the probability of successful cure.
For us, the public, we also need to minimise the probability of the virus being transmitted to us, and this means taking proper precaution not to have either direct or indirect physical contact with any other person, friend or stranger. If we succeed in doing so, we shall be able to reduce the transmission of the virus to virtually zero. This is possible if we are willing to adopt and maintain good hygienic behaviour and practices. For example, we should give up the Western custom of shaking hands, or kissing and hugging. Instead, we should revert to the traditional Chinese way of greeting, “Gongshou (拱手)”, that is, cupping one hand in the other before one's chest and moving them up and down all the while looking at each other’s eyes. It does not require physical contact, and can be done efficiently groupwise in a circular manner as well as pairwise. We should wear face masks, use disposable gloves when touching things in public areas, wash our hands with disinfectants or wipe them with alcohol regularly, and refrain from touching our eyes, nose and mouth with our hands. In time, we can introduce sensor-operated doors and voice-activated elevators so that physical contacts can be minimised.
The transmission of the virus will stop if everyone takes proper precaution for his or her own self-protection. With all of us taking measures to protect our individual selves, we also protect all others by helping to reduce the probability of secondary transmission to zero.
In any case, the fatality rate of the coronavirus is apparently not high, and so far the deaths caused by the virus are concentrated among high-risk groups such as older people and people with pre-existing health conditions. Nationwide, there have been 637 deaths out of 31,211 total confirmed cases, resulting in a fatality rate of 2.0%. However, the overwhelming bulk of the deaths attributable to the coronavirus has occurred in the Province of Hubei, with 618 deaths out of 22,112 total confirmed cases, and a fatality rate of 2.8%. In the whole rest of China, the total number of deaths is 19, out of a total confirmed cases of 9,099, implying a fatality rate of 0.2%. There has been only one death outside of China, in the Philippines (and one in Hong Kong), out of a total of 225 identified cases, or a fatality rate of 0.4%. (All numbers are as of the morning of 7 February.) These rates were all much lower than the 10 percent fatality rate of the SARS virus. They show that with the proper medical care, which has been generally available except in Hubei because of its very large number of cases, the fatality rate is very low. The fatality rate of Hubei is expected to come down significantly in the next couple of weeks as medical care becomes much more available now that new hospitals have come into service there. There is no need to panic.
The number of nationwide daily newly confirmed cases on the Mainland has begun to fall after a steep rise, from 3,256 on 3 February to 3,952 on 4 February, 3702 on 5 February and 3,151 on 6 February[1]. The bulk of the newly confirmed cases, 2,447, or more than 78 percent, is found in Hubei, where the initial coronavirus outbreak occurred. A large number of newly confirmed cases in Hubei at this phase of the epidemic is to be expected. It is actually a positive development, because it means that more and more previously unidentified cases are being identified. The new isolation hospitals entering service in Hubei at this time should help to reduce the number of unidentified cases there and hence further limit transmission of the coronavirus. For most of the places outside of Hubei, such as Changsha, Chongqing, Hangchou, Nanjing and Shenzhen, the trends all indicate a gradual decline from the end of January. The overall picture suggests that the spread of the coronavirus to areas other than Hubei has been largely contained.
The cumulative number of coronavirus patients cured on the Mainland has risen to 1,542, and exceeds the cumulative number deceased caused by the coronavirus, 637, as of 7 February[2]. Different cures from Germany, Thailand and the U.S., including “remdesivir” of Gilead Sciences, and of course from China itself have proved to be effective against the coronavirus. When there is a known effective treatment, there is really no need to panic. I believe the tide has turned.
Based on the model I used during the SARS epidemic, I would expect that the number of nationwide daily newly confirmed cases should begin to decline and will be in the hundreds by mid-February. I am reasonably confident that the coronavirus epidemic should be essentially over by the end of March, if not sooner.
Now that the virus has spread beyond China, potential unidentified patients can in principle come from almost anywhere, and not just from the Mainland. Even closing the border completely to the whole rest of the world will not stop the increase of new coronavirus patients in Hong Kong because of the existence of as yet unidentified patients. Working at home will help to reduce opportunities for transmission, but it can only be a temporary measure, and in itself will not stop the transmission. The proper way for us to deal with the possible spread of the coronavirus is for all of us in Hong Kong to take precautionary hygienic measures to make it impossible for transmission from unidentified patients to occur. All travellers to Hong Kong, wherever they come from, and whether they are permanent residents, should be monitored and required to undergo tests and if necessary quarantined. But if all of us continue to be properly cautious, there should be no new infected patients, and we would be able to stop the epidemic.
In time, hopefully soon, vaccines will be developed for the coronavirus and its variants. However, perhaps we should continue with our new behavioral and hygienic norms so as to avoid other infectious outbreaks in the future. And governments around the world should ban wild life markets, the source of both the SARS virus and the current coronavirus, permanently.
