Antibody tests have shown that 45 per cent of the dwellers in the capital were infected with the novel coronavirus. Of them, 24 per cent was above 60 years of age.
The study was published at a hotel in the capital's Gulshan on Monday afternoon.
After analysing the genes of the coronavirus, the researchers also assumed that the first COVID-19 infection happened in the country in mid-February.
The antibody tests found that 45 per cent of the city dwellers who had no symptoms of coronavirus were infected with the novel virus.
The study also found that about three-fourths of people in Dhaka's slums have already been infected.
Out of 129 wards of Dhaka north and Dhaka south city corporations, 25 were selected for the study on random sampling basis. A mahalla (locality) was chosen from each ward in the survey while 120 households from each mahalla.
Besides, eight slums were included in the survey.
Samples of the common households in Dhaka city were collected from mid-April to mid-July while samples of slum dwellers were collected between mid-July to the end of August.
Researchers said that this information will be useful for infection control, treatment and vaccination.
The research findings were revealed at the time when the issue of the second wave of infections is being discussed in the country.
Prime minister Sheikh Hasina earlier warned about the possible risk of increased infection in the upcoming winter season. On the other hand, the health ministry and the Directorate General of Health Service (DGHS) said they have all necessary of preparations to deal with the situation.
Researchers and scientists from IEDDR and icddr,b revealed their research results at the event. It was presided over by additional director general (planning and development) of the health department Meerjady Sabrina. Health minister Zahid Maleque joined the event online.
The study was jointly conducted by the government's Institute of Epidemiology, Disease Control and Research (IEDCR) and the private International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) and was funded by the United States Agency for International Development (USAID) and the Bill & Melinda Gates Foundation.