They are probably not catching even the majority of those with symptons let alone the asymptomatic ones.
In BD, they are testing only around 35,000 people a day with a population 2.5x that of the UK. UK tests I think around 1 million a day now.
All countries like Pakistan and BD can do is to catch the majority of those with symptons that are likely to be "superspreaders" and in high-hazard occupations like healthcare, and take them out of circulation to stop them infecting others.
BD has definitely turned the corner as new cases have been coming down for over a week now, and unless there the virus variants are totally different in Pakistan, then it is possible and I have every faith that the Pakistani government will do whatever it takes to bring this virus under control quickly.