Lockdown should be at least 14 days now, otherwise it won’t work – expert
There is a major deterioration in the global COVID-19 situation largely driven by outbreaks in South and South East Asia, warned world famous virologist, Prof. Malik Peiris.
Now there are outbreaks not only in India, Nepal, Bangladesh and
Sri Lanka but also in Malaysia and Thailand, this expert who was recently awarded the John Dirks Canada Gairdner Global Health Award for his work on the containment of SARS in 2003 and bird flu, said on Wednesday.
Looking closely at India before turning his sights on Sri Lanka, Prof. Peiris, Professor of Virology at the School of Public Health, Hong Kong University (HKU), told a Zoom meeting of the Organization of Professional Associations (OPA), that case numbe rs dramatically increased over the last few months there, following a marked reduction in the “stringency” of public health and social distancing measures. This was amplified by permitting very large gatherings of people for religious and political events.
The recent surge in India is attributed to: the relaxation of public health and social measures since October 2020; the low vaccination coverage; and the emergence of a more transmissible and concerning variant.
According to Prof. Peiris, only about 7% of India’s population has been vaccinated, who have even received a single dose. This is not very different to Sri Lanka. There has also been the emergence of a more transmissible variant of concern – B.1.617 (often called the ‘double mutant’), which has squeezed out all other variants very rapidly. This is the classic signal of a more transmissible virus. One of the variants it has replaced is the B.1.1.7, the so-called ‘UK variant’, which is responsible for the current surge of cases in Sri Lanka.
“We, therefore, have to assume that B. 1.617 may be even more transmissible than the virus currently wreaking havoc in Sri Lanka. Worse is the possibility that this B. 1.617 virus may be able to evade, at least partially, pre-existing immunity by natural infection and also by vaccination,” he said.
The Sri Lankan situation
Turning his focus to the Sri Lankan situation, Prof. Peiris said that when looking at data, one finds COVID- 19 positive cases in every province with an increasing trend in most provinces. Limiting travel between provinces is not likely to be of relevance any more. Maybe, if they had been introduced in midApril, they might have had an impact reducing the spread of B. 1.1.7 out of the Western and North Western Provinces, but not now.
How do lockdowns work?
The propagation of an epidemic occurs when one infected person comes into contact with other people and the virus may transmit to some of them. What is achieved with the “lockdown” is that you compartmentalize these infected people into households or small units, said Prof. Peiris.
His explanation is: “Then, this person would possibly transmit the disease to others in the household. Hopefully most of them will be mildly symptomatic or asymptomatic. If somebody is seriously ill that person will be taken to hospital. But these people will rapidly develop immunity and soon the virus runs out of new people to infect and dies out. A virus cannot survive if it does not have new non- immune people to infect.
As long as these infected people are confined to one household, the virus has no chance of spreading further. Once the virus runs out of people to infect, it ‘burns out’.
“The next question is how long this confinement or ‘lockdown’ will have to be? Overnight? Obviously not. The science is based on the period of infectiousness of an individual and the incubation period of the illness. We know that the period of infectiousness of an individual is 5 to 7 days. If he/she is infectious at the beginning of a three-day lockdown, he/she will remain infectious at the end of the three-day lockdown and will be out in the community on the fourth and fifth days, continuing to spread the virus.”
The incubation period is the number of days from getting infected to developing symptoms and/or becoming infectious, explained Prof. Peiris, pointing out that the median is about 5 days.
“If a person in a household is infected and there is a lockdown, he/she may transmit the disease to other members. This interval on average would be around five days for these people to get infected and become infectious. Thereafter, for them to become non-infectious it will take a further 5-7 days. This is why a lockdown has to be at least 14 days to break the chain of transmission. This is also why three-day lockdowns are going to have minimal effect,” he added.