The National Institute of Health (NIH) announced on Monday that the first case of Omicron sub-variant BA.2.12.1 had been detected in Pakistan.

The institute — which has been looking after Covid-related matters since the National Command and Operation Centre was formally shut down — said the sub-variant was causing an "increasing number of cases in different countries".

"The best preventive measure (besides mask-wearing at crowded places) is Covid-19 vaccination. We strongly recommended getting vaccinated and all those due for boosters must get the shots immediately," the institute added.

The new Omicron sub-variant is a descendant of the earlier super-contagious “stealth Omicron” and has quickly gained ground in the United States.

BA.2.12.1 was responsible for 29 per cent of new US Covid-19 infections in April's third week, according to data reported by the US Centres for Disease Control and Prevention. And it caused 58pc of reported infections in the New York region.

The variant has been detected in at least 13 other countries, but the US has the highest levels of it so far. Scientists say it spreads even faster than stealth Omicron.

The development comes as Pakistan is witnessing a decrease in the number of Covid-19 cases which have dropped significantly during the past few weeks.

Less than 100 Covid-19 cases have been reported on a daily basis since April 27, with the country reporting only 64 cases on Monday.