There is no standard definition of a first and a second wave of a pandemic. The first wave of a pandemic is generally referred to as a sudden surge in cases clearly at a rate that is above the baseline and exhausts the health system.
A decline in the first wave, often for months, followed by a surge in cases is considered as a second wave. The concept of waves of a pandemic has often been linked to the last influenza pandemic in 1918-19, which had three waves, with the second being the worst.
The novel coronavirus causing the current pandemic is very different from the influenza virus. First, these two viruses belong to two different families of viruses. Secondly, influenza is a seasonal virus (winter virus) which goes away with a change in the season and comes back the following year and hence causes waves of seasonal outbreaks.
From the data available so far, there is no evidence yet that SARS-CoV-2 is a seasonal virus, although there can be an increase in transmission during winter months as people move indoors and there is heightened physical interaction. It is possible that SARS-CoV-2 will not follow a seasonal pattern, rather, there will be phases of flattened curve followed by small bumps.
While the world is still in the first wave of the pandemic, some countries including Australia, New Zealand, Vietnam, Hong Kong, Germany, Singapore, and South Korea have been able to contain their first waves through strong public health control measures and exhaustive testing and tracing regimes.
As these countries start to ease of lockdowns and restrictions around social gatherings, and open up borders, it is likely that there will be small spikes in the number of new Covid-19 cases or even a cluster of cases.
However, if these countries can ensure testing, tracing, and isolation of all new suspected cases and quarantining contacts of cases through strong public health infrastructure, these small spikes can be suppressed.
In some instances, if the number of new cases surges rapidly, like in Victoria, Australia, there may even be re-enforcement of social restrictions and (limited) lockdowns to curtail transmission.
Till a vaccine becomes available, this may be the “new normal” for many countries.
Where is Bangladesh in regard to the first and second waves of the pandemic? An increase in the daily number of testing and a contemporaneous decline in the number of newly identified Covid-19 cases gives us an indication of the containment of the first wave of the pandemic.
The absolute numbers of daily testing and the daily test positivity rate in Bangladesh have plateaued for weeks, which not only raises scepticism about the data, but also makes any prediction difficult.
Even in the absence of an optimal level of testing and robust data, it is clearly evident from the current trend of Covid-19 cases in Bangladesh that the country is very much in the middle of the first wave.
As Bangladesh moves to a premature easing of restrictions and lifting of lockdowns before containment of the first wave, it is imperative that the country continues to re-enforce other proven control measures such as repeated hand-washing, avoiding touching the face, staying home when sick, and wearing a face mask in public places.
Lastly, Bangladesh has to step up its testing and tracing capacities if the country has any expectation to suppress the first wave and prevent the resurgence of a second wave of the Covid-19 pandemic.
Dr Nusrat Homaira, PhD, is a Senior Lecturer (Respiratory Epidemiology) at UNSW, Sydney, Australia.
