45% of Dhaka exposed to coronavirus

According to a study, 45% of Dhaka residents have developed antibodies for Covid-19, meaning they have already been exposed to the novel coronavirus, SARS-CoV-2 .

Another study found evidence that the novel coronavirus arrived in the country in mid-February, though the first cases of Covid-19 in the country were confirmed on March 8.

The studies were unveiled in a seminar jointly organized by the Institute of Epidemiology, Disease Control and Research (IEDCR), and the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), in Dhaka on Monday. The studies were funded by USAID and the Bill & Melinda Gates Foundation.

In his presentation, Mahbubur Rahman, Assistant Professor of epidemiology  with IEDCR, said serology tests have shown that some form of Covid-19 antibodies are present in 45% of the respondents to the study in Dhaka. Of them, the highest proportion were over the age of 60.

He added that the respondents were divided into two broad categories: residents of Dhaka city, and residents of Dhaka slums.

928 persons, including 400 from symptomatic households and 528 from asymptomatic households, were tested thrice over the 28-day research period.

“9.8% people tested Covid-19 positive, with almost no difference between the genders (males 9%, females 10%),” Assistant Professor Mahbubur said.     

6% of the cases were symptomatic and 94% were found to be asymptomatic. 

Of the asymptomatic cases, 12% of the respondents have developed symptoms recently, taking the number of symptomatic cases to 18%.

74% of slum dwellers have developed antibodies

In another presentation, icddr,b Senior Scientist (Infectious Diseases Division), Dr Firdausi Qadri, said although an overall 45% of the respondents were found to have developed some sort of antibodies, the prevalence of antibodies among slum dwellers was found to be at 74%.

For this research, samples were taken from 333 symptomatic people and 359 asymptomatic people in the city, while the sample size for slums was lower, at 125 (36 symptomatic and 89 asymptomatic).

She said: “The encouraging rate of seropositivity suggests the onset of herd immunity.”

Epidemiologist Mustuq Husain said the prevalence of antibodies in over 60% of the population is considered herd immunity.

However, ASM Alamgir, principal scientific officer (PSO) of IEDCR, said the sample size for slum residents is too low to make definitive conclusions.

“We cannot say antibodies alone will build herd immunity. However, antibodies along with vaccination may help develop herd immunity,” he added.

Additional Director General (Planning and Development) for the Directorate General of Health Services (DGHS), Professor Meerjady Sabrina Flora, said: “It will take a long time for a Covid-19 vaccine to come to market, so we all have to be careful by wearing masks and following health guidelines, o as not to bring a second wave of Covid-19 in the country .”

Coronavirus arrived in February

IEDCR Director Dr Tahmina Shirin, in her presentation, said genomic analysis has shown that the novel coronavirus likely arrived in the country in mid-February.

She said the study analysed 392 samples (67 collected and 325 deposited at GISAID) from March 8 to July 5. During their analysis, they found that at least 19 distinct SARS-CoV-2 lineages, having mutated, were circulating at the time of analysis.

The IEDCR director added that they took three main lineages as samples for the genomic study, of which B.1.1 and B.1.1.25 had circulated in eight divisions of the country, and B.1.36 circulated in Chittagong only.  

Minister for the Ministry of Health and Family Welfare, Zahid Maleque, and icddr,b acting executive director Tahmeed Ahmed, also participated in the program, among others.