A science-based strategy to control the current COVID-19 situation

 The vaccination program, currently getting under way within the constraints of limited vaccine supply, will take many months to translate into an impact on mortality – Pic by Shehan Gunasekara

•   A document developed for decision-making 

By Malik Peiris and Kamini Mendis

I. The current COVID-19 situation in the country 

There is a high intensity of transmission of COVID-19 in the country just now. Although it became apparent with cases increasing in the last week of April, the increase in transmission began about four weeks before that. 

The incubation period of the virus (three to 14 days) together with testing/reporting delays mean that the cases detected and reported now were the result of transmission that took place one to two weeks ago. Since deaths follow with a lag period of a further two weeks, the deaths occurring now were the result or transmission that took place one month ago. 

The B.1.1.7 variant of the virus spreading now is more transmissible, and possibly more virulent, than in previous “waves”. An even more concerning variant B.1.617 (first detected in India) has also been detected in Sri Lanka and it remains to be seen how widespread it will become. 

There was an exponential increase of cases from mid-April to date. Although case numbers appear to plateau in recent days, it is likely that this is a result of limitation in testing capacity. Testing numbers have remained flat, in spite of high positive rates (exceeding 10% in most laboratories), raising concerns of whether the epi-curve we now see reflects reality. ICU admissions and deaths continue to increase, as will be inevitable, from infections that have already occurred. 

As a result, the capacity of the health system to manage COVID-19 patients has already been exceeded, the inevitable consequences being more avoidable deaths. With increasing cases, even the implementation of the public health measures that were being implemented – i.e. testing, isolating, contact tracing and quarantining have exceeded the capacity of the health sector. In addition, health staff in the curative and preventive sectors is becoming victims of COVID-19 themselves, which makes the situation grave. 

The vaccination program, currently getting under way within the constraints of limited vaccine supply, even if targeted to those at highest risk of death, i.e. the elderly and those with co-morbidities (a policy that has NOT been consistently followed in Sri Lanka so far), will take many months to translate into an impact on mortality. Vaccines, which require two doses at least a month apart, take optimal effect >2 weeks after the second vaccine dose. 

As of now, only 1% of the population have received both doses of vaccine and 6% received at least one dose, that too, in one province of the country. Even under the most optimistic scenarios, it will be over six months before most of the high-risk population receives protection from vaccine across the country. 

The only available option in the short-medium term to arrest this impending catastrophe is to significantly curtail transmission through social and public health interventions.

Although a few public health interventions have been implemented in the past week, we explain below why these recent measures of small-area isolations, prohibiting inter-provincial travel, intermittent and short period lockdown as the one during 14-17 May, together with mild restrictions on human movement such as those based on identity card numbers, will not arrest this wave of the epidemic. 

We explain why a nation-wide lockdown (defined below) is absolutely necessary, if increasing ICU admissions and deaths from this wave are to be contained. We assess the likely economic impact of these different approaches. 

II. Why small-area isolation, preventing inter-provincial travel, short and intermittent lockdowns and mild restraints on human movement will not work 

1. The testing is not sufficient to make small area isolation have an impact

Small area lockdowns are based on obtaining information of a cluster(s) of cases from a particular location. The detection of these clusters are based on testing a population in an area in response to detecting a few cases from that location – i.e. reactive case detection rather than proactive surveillance. Thus, by the time the cluster has been detected, multiple weeks have lapsed since the initiation of each cluster and therefore the people in that cluster would have already spread the virus through their movement, to many other areas. In other words, isolating that small area will not have much effect on the spread of the virus to other areas, because it has already happened. If small-area isolation is to work, then an extensive amount of active surveillance and testing in the population (as opposed to being based on contact tracing) is necessary, but this is currently not feasible given the laboratory system being already overloaded. Initiating these small-area lockdowns are sucking up a huge lab testing capacity at the moment, which will be more productively deployed elsewhere. 

2. Since all provinces have ongoing high transmission already, stopping travel between provinces will have little effect

By the end of April, all provinces had ongoing high transmission of the virus and therefore stopping inter-Provincial travel will be of no avail at this stage. It may have had a role in early or mid-April, soon after the B.1.1.7 variant was detected in the Western Province. But not anymore, with the virus entrenched in every province. 

3. Countrywide lockdowns of three days will not block even a single cycle of virus transmission 

Intermittent countrywide lockdowns such as the one from 14-17 March will only have effect during those three days. Three days is far shorter than the incubation period of the virus, i.e. from infection to manifestation of illness and transmission, which is around five days (range three to 14 days). It is even shorter that the infectious period of one infected individual, which is around 10 days. In order to even partially interrupt transmission, one needs to cover at least two cycles of transmission, i.e. 10-14 days of intervention. Therefore, the minimum period of lockdown should be country-wide and at least two weeks in duration. 

4. Partial restriction of human movement using ID card digits will not have much impact on virus transmission

Limiting the movement of people and crowd-gathering through means such as restricting them to alternate days based on identity card numbers is not sufficient to prevent the congregation of people because up to half the population could be out of home at any given time. This is not sufficient for transmission is to be halted. 

5. Standard preventive measures are not having optimal impact because of overcrowded living conditions

Even the strict enforcement of social distancing and mask wearing will not have its optimal impact because they are not ideally implementable under overcrowded living conditions in urban areas. 

6. People working in enclosed environments e.g., office spaces will enhance virus transmission

Offices such as banks, and industrial working places such as garment factories require people to be in enclosed and confined spaces with insufficient ventilation for the entire working day. These are an extremely and highly conducive to the spread of the virus. 

Thus, these recent measures have impeded economic activity for a minimal public health gain at best. Moreover, repeated, intermittent short-duration restrictions will not achieve the public health goals. This is because the uncertainty associated with the introduction of these measures/future measures create an unstable environment for most economic activities.

Most daily-wage earners are not given work by employers because they travel to work daily from unknown risk situations at home, and therefore the perceived high risk of transmission. Most industries and offices are working within a context of uncertainty and are unable to plan even for the medium-term. This is not conducive to economic growth. 

A rational, determined and convincing strategy is needed, both to get control of an impending public health disaster and also to restore economic confidence. 

III. A countrywide lockdown for at least 14 days is immediately necessary for the following reasons

1. Only a degree of restriction of human movement enabled by a total countrywide lockdown of 14 days will lead to interrupting at least one (preferably two) cycles of virus transmission in the community. Such an intervention would give an opportunity for the health sector, currently at or beyond breaking point, to catch its collective breath, to face the future. Otherwise, exponential increase in the number of cases (and deaths) will lead to health staff succumbing and the consequent collapse of the health system. 

2. Such an intervention can be signalled >5 days in advance so that the community, traders and businesses can make adequate preparations. It will give some level of certainty and instil confidence in the population, the business community and the health sector. 

3. The daily wage earners will need to be given an allowance to tide over this period. But this investment will be amply repaid by the opportunity to get control of an epidemic that is rapidly spiralling out of control. 

4. Access to essential commodities – food, fuel, medicines, healthcare will not be compromised because the necessary logistical arrangements can be made. The experience of the March-April 2020 lockdown will be an asset in planning and implementing the distribution of essential goods to the people. 

We recommend the following:

All persons to remain in their homes at all times for a period of at least 14 days, and all schools, industries, commercial enterprises and places of worship to remain closed, with the exceptions listed below. These exempted places will be subject to social distancing, capacity restriction, wearing of face-masks, hand sanitising and operating under conditions of optimal ventilation. 

1. All essential services to be functional. 

2. A minimum number of grocery stores, pharmacies, and fuel station to remain open in every district. A limited number of vegetable, fruit and fish/meat, bakery and other food delivery vehicles permitted to operate on the basis of permits. 

3. Restaurants able to prepare food for delivery on order, but not allow in-house dining. 

4. Government departments deemed essential, to keep an office open for a few hours a day and function with a skeleton staff on a roster basis. 

5. Any organisation or enterprise may allow its employees to work from home. 

6. A person can leave home only for a health need, any other emergency, or to purchase food supplies, but only one person can leave home at any one time for these purposes. 

7. Gatherings of more than four people to be prohibited. 

8. Outdoors agricultural work permitted to continue. 

We request, in addition, that all ongoing preventive measures be enforced rigorously, including increasing vaccination coverage, and that case management and treatment interventions are greatly strengthened in the country.  

(Malik Peiris is Chair/Professor, School of Public Health, University of Hong Kong, Faculty of Medicine, Hong Kong. Kamini Mendis is Professor Emeritus, University of Colombo, Public Health and Malaria Expert formerly at the World Health Organisation.)