While the authorities maintain that community transmission is happening only in clusters and that there is nothing to worry, experts say unless the government draws up a cluster containment strategy immediately, the situation will remain worrisome.
The implementation of the strategy will help contain Covid-19 within a defined geographic area by detecting cases early and breaking the transmission chain, preventing further spread of the highly contagious virus, they said.
The term "cluster transmission" is used to identify infections that are largely concentrated in a limited locality, often within a family and its extended circle.
Experts said discovering a cluster is akin to a fire alarm going off and every moment wasted will increase the chances that the fire may spread. The faster the infected individuals are identified and sent into quarantine, the lesser are the chances of future cases.
On Sunday, the Institute of Epidemiology, Disease Control and Research (IEDCR) said that community transmission of coronavirus was indeed happening, but it was limited to five clusters across the country.
But nothing about the size of the clusters was mentioned -- whether those were consisted of a few individuals, a few households or an entire community which is potentially at risk of contracting and spreading the coronavirus.
The experts said the government must take strict actions, including enforcing lockdown of the clusters, and that any delay in doing so would only make things worse and the situation might get out of hand.
They talked about India for an example. The country is currently enforcing a strict lockdown of communities or neighbourhoods of Covid-19 positive clusters.
But there has been no such strategy in Bangladesh yet and it is almost entirely up to the local administration to handle the situation as they see fit, they said.
Talking to The Daily Star, Be-Nazir Ahmed, former director of (disease control) at the Directorate General of Health Services (DGHS), said the government should act immediately and strictly to bring the cluster transmission to zero.
"Lockdown should be enforced but at the same time epidemiological intervention is a must," he said.
He suggested that geographic quarantine, social distancing measures, enhanced active surveillance, testing all suspected cases, isolation of all cases, quarantine of contacts and a well thought out strategy should be adopted.
"If this intervention is successful then it can be replicated in other places or if there is any error that can be addressed. But the point is if we fail to contain it at the cluster level, the situation will be out of control," he warned.
In India, the health ministry adapted to a cluster containment strategy to contain the disease within a defined geographic area by early detection of cases, breaking the chain of transmission and thus preventing the spread of the virus.
Replying to a query, DGHS Director General Abul Kalam said, "We are learning new things every day. We will do whatever needed to contain the spread of Covid-19."
Asked whether any strategy was already adopted aiming at the cluster level, he said, "Not yet, but [it] will be soon."
Officials at the DGHS and the IEDCR declined to say how many people were traced and tracked as suspected cases following identification of confirmed Covid-19 patients.
Prof Mozaherul Huq, former regional adviser of World Health Organization's (WHO) South East Asia region, said the immediate need now is to lockdown certain areas and then trace and track those who might came in contact with coronavirus patients.
"Following enforcement of the lockdown, all the people in that area should be tested. If anyone tests positive, that person should be sent into quarantine. For the cluster system, institutional quarantine is must," he said.
Many countries have discovered a large cluster and in most of them, the number of Covid-19 cases shot up after identification of the infected and contact tracing began.
Till April 4, South Korea has mapped 83 percent of its cases to some clusters. More than 51 percent of the country's cases originated from the Shincheonji Church of Jesus. And most of the infections were allegedly brought to the church by a 61-year-old woman who ignored her symptoms and attended the church, according to international media.
In Austria, the Ischgl Ski Resort is said to have been linked to 600 cases.
A funeral in George Town, Albany, US may have resulted in more than 600 infections.
The Osaka Live Music Venue in Japan is directly linked to 80 cases.
A dinner party in Singapore is linked to 43 cases, according to media reports.