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News Analysis: What does our Covid-19 testing tell us?

  • Published at 02:09 pm April 10th, 2020
Web_Coronavirus test_Mahmud-Hossain-Opu
Photo: Mahmud Hossain Opu/Dhaka Tribune

Bangladesh has seen a rapid rise in coronavirus cases in April

Bangladesh recorded its first case of Covid-19 on March 8. Thereafter, the disease initially spread slowly, and by month’s end there were still only 51 cases countrywide. As far as we know.

However, the month of April has seen a rapid rise in cases, with the number of cases rising to 424 as of April 10, a 29% rise from the day before and nearly 700% rise from the start of the month.

This rise can be explained by two things: the first is that typically the infection curve starts to rise steeply between three to five weeks from the first recorded case. In some countries this has happened quicker, and in some countries slower, but Bangladesh would seem to be squarely on track with respect to the global experience.

The second reason is that we have only recently ramped up our testing, and there is every reason to believe that our rising case-load in large part simply reflects the fact that we are testing more people than before.

In Week 1 following the first reported case, Bangladesh tested just 100 suspected carriers, in Week 2 the number was 204 and in Week 3, 574, still fewer than 100 per day. It is only in the last few days that testing has been ramped up, with 1184 tests being conducted yesterday, the highest number yet.

In addition to the fact that we are now testing more is the fact that we are now testing outside of Dhaka. This means that more cases are being detected outside of Dhaka.

However, testing outside of Dhaka still lags behind testing inside Dhaka, leading to fears that cases outside the capital are being dramatically undercounted.

On April 10, 701 tests were conducted in Dhaka, whereas only 483 tests were conducted in the entire rest of the country put together.

Of the 94 cases detected on yesterday, fully 37 were in Dhaka, with 16 in Narayanganj, and only 41 in the rest of the country.

The confirmed cases are therefore likely just the tip of the iceberg, and as we continue to ramp up testing, this number is likely to continue to shoot up.

However, we need to also recognize the limitations of our testing regimen.

Even with testing crossing 1,000 threshold a day, we still lag far behind where we need to be. Bangladesh’s testing to population ratio is one of the lowest in the world, and even with a massive increase in testing, is likely to remain so.

Of course, no country can test everyone, but even if there are many uncounted cases, if a country employs a steady strategy of who it is testing, this works to provide a stable sample, and a rise or drop in the number of cases can provide useful information. However, neither is that happening in Bangladesh, which is why the increased testing is only of limited use.

It needs to be kept in mind that cases can be divided into three categories: asymptomatic cases, symptomatic cases that are not tested, and symptomatic cases that are tested. Testing only tells us the number of people in the third category, not the number of people overall who have or have had the virus.

There is no question we should be testing much more, especially outside Dhaka. The more information we have at hand, the better we can plan.

But for the foreseeable future, the number of reported cases will tell us very little about the actual prevalence of Covid-19 in the population at large.

The best strategy is to test as many people as possible. The more you test, the better your information.

Equally clearly, that won't happen in Bangladesh.

The second-best strategy is to ramp up to several thousand tests per day at a bare minimum, and, more importantly, then hold this number and the testing strategy and parameters steady.

Only then will our testing give us the kind of workable information we need both to gain a picture of where things stand in the country and therefore what strategies we need to employ moving forward.

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