A preliminary data of a government survey shows that about one in 10 people in Dhaka city are Covid-19 positive and most of them do not know about their condition, raising the chances of spreading to others.
It vindicates the government’s policy of making mask wearing mandatory for all along with social distancing measures to prevent the spread of the virus.
The survey also found that the prevalence of COVID-19 cases was “significantly lower” in slums than the overall estimate of Dhaka. But the researchers did not look into the reasons for that difference.
The government’s disease monitoring agency IEDCR conducted this ‘cross-sectional household survey’ between April 18 and July 5 in both Dhaka north and south city corporations with the help of icddr,b. The USAID and Bill and Melinda Gates Foundation (BMGF) supported the initiative.
“We conducted this survey to understand the burden of the disease,” Prof Meerjady Sabrina Flora, IEDCR director, told Bangladesh Post.
“We always present positive cases only from those who come to test. But to understand the burden in the community, we needed this survey,” she said.
“One in 10 people infected are not less. But still I think the findings are nothing unusual. Our daily positive rate (out of the tested samples) was close to it and the hospital admission we see is also less. We always say most of the cases are mild,” she said.
Mostly asymptomatic
The survey found that overall 9 percent among all individuals in Dhaka on the day of the visit was estimated as Covid-19 positive.
The IEDCR gave further analysis of the figure and said 5 percent of the total households were symptomatic, and 2 percent of the total populations were symptomatic.
It also said 30 percent of the symptomatic individuals, 14 percent of asymptomatic individuals from symptomatic households (household contact) and 8 percent of the asymptomatic individuals from asymptomatic households had COVID-19.
Bangladesh Post analyzed the data and by a gross calculation found that over 90 percent of the cases were asymptomatic.
If we think 100 households, of them, according to the IEDCR, five households were symptomatic, which means that 95 households were asymptomatic.
If we consider, four members in a household which means that 20 people were in the symptomatic houses and the rest 380 people were in asymptomatic houses.
And 2 percent of symptomatic means eight people of the 400 are symptomatic which means those 8 people came from the 20 people in symptomatic houses.
So the rest 12 people in those symptomatic households are asymptomatic from the symptomatic households.
And 8 percent positive were found from those 380 asymptomatic people in asymptomatic houses.
A gross calculation gives the figure that only 7 percent were symptomatic and the rest 93 percent were asymptomatic.
Determine further course of action
Dr Shams El Arifeen, a director of the icddr,b, who was involved with the survey told Bangladesh Post that he was “not alarmed” by the result, when asked.
“This is an important piece of information. Now experts should sit together to determine the further course of action,” he said.
When asked, he said, “Yes, we have a large number of cases asymptomatic which means the government’s provision of mandatory mask wearing should be implemented.
“It’s because we don’t know who is infected. I even don’t know since I don’t have any symptoms”.
He said in India over 80 percent Covid-19 patients did not have symptoms.
“We need to implement the government policy of mask wearing strictly,” he commented.
Survey details
A total of 3227 households were visited, and 211 symptomatic individuals were identified, of which 199 were tested with real-time RT-PCR.
A total of 435 asymptomatic individuals were selected from symptomatic households, of which 201 were tested and 827 asymptomatic individuals were selected from asymptomatic households, of which 538 were tested.
An additional sample was collected from 6 slums in Dhaka city (720 households).
The prevalence of COVID-19 cases was 6% among slum dwellers, which is “significantly lower” than the overall estimate of Dhaka, according to the IEDCR.
The prevalence of RT-PCR +ve COVID cases was highest among people aged 40 years and over (13%) and adolescents aged 15-19 years (12%).
The prevalence was 6% among children aged less than 10 years.
Among the COVID-19 cases, who had symptoms, 93% had a fever, 36% had a cough, 17% had a sore throat, and only 5% had shortness of breath on the day of testing.
Among the COVID-19 cases, who had symptoms, 15% were hospitalised. Only one death was reported among all COVID-19 cases with one month of follow-up. The deceased individual was symptomatic and hospitalised.
The households were categorised as symptomatic and asymptomatic based on this initial screening.
If any household members had any of the four COVID-19 symptoms on the day of the survey or within7 days preceding the survey, the household was considered as a ‘symptomatic’ household.
If none of the household members had any of the four COVID-19 symptoms on the day of the survey and within the 7 days preceding the survey, the household was considered as an asymptomatic household.
All symptomatic households and approximately every tenth asymptomatic household were selected for laboratory testing, according to the IEDCR.
