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Are we entering the fourth Covid-19 wave?

By Dr. Charuni Kohombange 

The Covid-19 pandemic, the defining global health crisis of our times, is still continuing across the globe. According to present data, Southeast Asia is becoming the global epicentre for the most virulent Delta variant of the virus. While Thailand reported a record number of cases early this week, Malaysia has also notched up over one million cases. Meanwhile, Singapore is seeking possibilities to allow quarantine-free travel for fully vaccinated travellers, as they expect to inoculate 80% of their population by September.

In Sri Lanka, the average number of new cases has increased over the past few days. At the time of writing, Sri Lanka reported 1,450 new cases per day on average and the total number of deaths has exceeded 4,150.

Meanwhile, Sri Lanka has administered over 8.9 million doses of the Covid-19 vaccines so far. In this context, some experts predict that we are entering the fourth wave of the pandemic.

This article aims to clarify these doubts through interviews with University of Colombo Professor in Community Medicine Manuj C. Weerasinghe, University of Rajarata Professor in Community Medicine Suneth Agampodi, and Sri Lanka Medical Association (SLMA) Immediate Past President and Organisation of Professional Association (OPA) Vice President Prof. Indika Karunathilake.

Following are excerpts of the interviews.

Some medical professionals state that Sri Lanka is on the verge of the Covid-19 “fourth wave”. Do you agree with this statement and how do you interpret the current situation?  

One recurring and sensational theme for Covid-19 coverage by the media are firm predictions of second, third, or fourth waves of the epidemic – this at times, without considering the appropriateness of forecasting waves in a coronavirus pandemic. We frequently see officials and organisations  try to base their decisions depending on the “waves”.

The term “wave” comes from the 1889-92 Spanish Flu outbreak that had different phases which are supposed to have occurred over multiple years. The pandemic infected 500 million people worldwide and killed an estimated 20 to 50 million people. The virus first appeared in the spring of 1918 but appears to have mutated when it surged again in the fall, making for a deadlier second wave.

According to WHO, “in order to say one wave is ended, the virus has to be brought under control and cases have to fall substantially…Then for a next wave to start, there should be a sustained rise in infections”. This pattern is yet to be observed during the current surge. In fact, Sri Lanka never really had a first wave. What was observed till late 2020 was a series of clusters separated by time and location. 

Therefore, making absolute statements of certainty about “waves” is unwise, given the current substantial uncertainties and novelty of the evidence. The entire debate over whether or not we will see a fourth wave is premature. We should not get caught up in whether there’s a wave or not because that misses the whole point. The focus now should be actively preventing the current outbreak. What is rational is to focus on control of the epidemic by following public health principles and scientific approach.

Can we be satisfied with the current PCR testing and reporting?

The timely and orderly reporting of PCR results is needed to gain insights into decision-making in controlling transmission, reducing mortality through identification of vulnerable groups, and evaluating the productivity of the decisions taken for control of the disease.

However, officially published data may not represent the actual Covid-19 status of the country due to inherent factors such as the incubation period of the disease and the natural history of the disease progression, as well as due to others such as delay in presentation, delay and under-reporting of confirmed Covid-19 cases and deaths, PCR backlog, etc.

What is the most important data for interpreting the current situation and predicting the future, and how do you use this data in an effective manner?

In Sri Lanka, currently, community Covid-related data is relayed through 352 medical officers of health (MOHs) and hospital-based Covid-related data is fed to the system via hospitals and laboratories, both in the state and private sectors. This data is relayed to the regional epidemiologist and the Epidemiology Unit, from where data is relayed to the State Intelligence Service (SIS) and is also utilised for hospital allocation and decision-making purposes by the designated personnel.

The limitations in this system are delays in relaying data from the primary data sources, differences in reporting formats used by different regions, information from all laboratories and all samples not reaching the upper levels of the system, etc. Similarly, delays in PCR reports and their backlog, delaying death reporting, etc. can be seen. Data regarding hospital allocation, division of hospital beds, the numbers managed through home-based management, intensive care unit (ICU) utilisation, and the oxygen need of patients is not included in this system and therefore hinders interpretation and decision-making regarding the current Covid-19 status in the country. This data is relayed through a separate data flow system; thereby, not only does it complicate data interpretation, but it also increases the workload of the personnel involved in this data management system.

A lag period between the reporting of cases and reporting of deaths is seen. This is due to the presence of a period between the occurrence of severe forms of disease, its complications, and the deaths. As a result, the wave of deaths follows the wave of cases by about three to four weeks.

Similarly, the deaths that are reported on a particular day are due to infections that took place over a range of several weeks. It depends on individual immunity, virulence of virus, access to healthcare, other risk factors, age, etc. Therefore, the number of deaths occurring on a given day should be updated as they are confirmed and reported, as opposed to the current system used in the country.

With the limited testing, the number of cases is likely under-reported and does not reflect the real situation at the ground level – the high rates of positivity in RT-PCR tests that are done, the death rates, and hospital admissions.

Considering all these limitations, the “trend” of cases and deaths provide better information for decision-making and evaluation of the methods to contain Covid-19. The reported numbers in terms of both cases and deaths can be less than the actual numbers due to non-detection of cases in the community, under-reporting, delays in reporting, and PCR backlog. Therefore, a weekly average showing the trends of the disease behaviour will provide the best information for decision-making.

The national strategy should set data standards and improve surveillance of cases and deaths so that a co-ordinated response could be set into motion.

With regard to the vaccination rollout, can we be satisfied with the current practice and the rate of vaccination?

The increase in the rate of vaccination due to increased supply of vaccines is very commendable. There is a need to focus the priority on preventing deaths of highly vulnerable sections of the population such as the elderly, health workers, and those with comorbidities. It’s important to revisit and revise the initial vaccine rollout plan.

Have travel restrictions that were imposed recently caused a positive impact on curbing the disease?

Mobility data, number of reported cases, and test positivity rate, when analysed together, show a positive impact. Mobility data is freely available through Google Community Mobility reports updated regularly. Change of mobility, for example, at retail and recreational spots, grocery, and pharmacy as well as the use of public transport shows an inverse proportion with the incidence of Covid-19 cases.

This is illustrated by the featured graph. It has to be noted that there is a lag period of two weeks (similar to the incubation period) between increased mobility and the increased number of cases.

With analysis of the current data, how do you foresee the country’s situation during the next few months?

It is very difficult to make accurate predictions due to the aforementioned limitations in the data flow. One of the reasons that Covid-19 is so hard to predict is its power to change the trajectory. It is also essential to gain a deeper understanding of mutant strains and their pathogenicity. Without this information, predictions become very subjective.

Further, the chaotic nature of epidemics and their consequent disruption should lead us to be cautious about forecasting the future. We do not know for certain whether Covid-19 will recur in phases, sporadic outbreaks, or disappear altogether.

The future scenario will depend on many factors such as the stringency of mobility restrictions, vaccine rollout, emergence of new strains, and, most importantly, adherence to preventive measures.