Close to 141,000 people died as a result of Covid-19 in Bangladesh between 2020-2021, as per WHO estimates – a figure much higher than the official count of some 29,000.
Fresh WHO estimates show that global Covid-19 deaths, in a 24-month period, were approximately 14.9 million – more than double the official death toll of over six million.
At the end of last year, only 5.4 million were reported.
The UN health agency's Director General Tedros Adhanom Ghebreyesus described the calculated figure as "sobering."
A study, by a team from the influential Institute of Health Metrics and Evaluation (IMHE), put the Bangladeshi death toll from Covid-19 at a whopping 413,000 – 15 times higher than the official figure.
However, a Bangladeshi government official at the time dismissed it as "speculative."
In Bangladesh, excess mortality was found to first spike particularly in the June-July-August period of 2020, when the WHO estimates an extra 30,000+ people died than would have been expected under normal circumstances.
Excess mortality is calculated as the difference between the number of deaths that have occurred and the number that would be expected in the absence of the pandemic based on data from earlier years.
At the end of the pandemic's first year, there were 46,041 excess deaths in Bangladesh.
During the second year, the months of April (14,276 excess deaths), June (13,013), July (20,030) and August (18,915) were the most difficult.
April 2021 is when the dreaded Delta variant of the deadly virus is suspected to have entered Bangladesh.
By December last year, the excess deaths in Bangladesh had accumulated to reach 140,764, WHO estimated further.
These number includes deaths either due to the coronavirus directly or because of factors somehow attributed to the pandemic's impact on health systems, such as cancer patients who were unable to seek treatment when hospitals were full of Covid patients.
It also accounts for poor record-keeping in some regions, and sparse testing at the start of the crisis.
The estimated number of excess deaths can be influenced also by deaths averted during the pandemic due to lower risks of certain events, like motor-vehicle accidents or occupational injuries as a result of lockdowns and working from home.
According to the WHO report issued Thursday, most of the Covid-19 deaths occurred in Southeast Asia, Europe and the Americas,
In India, there were 4.7 million Covid deaths, it says - 10 times the official figures - and almost a third of Covid deaths globally.
The New York Times reported in mid-April that the release of the WHO's report was being delayed due to objections from the Indian government. It was due to be released in early April.
The Indian government has said it has "concerns" about the methodology, but other studies have come to similar conclusions about the scale of deaths in the country, and estimates for worldwide excess mortality have been even higher than the WHO's.
The WHO's estimates include a breakdown of excess mortality by age and sex for the 24-month period from January 2020 to December 2021.
They confirm that the global death toll was higher for men than for women (57% male, 43% female) and higher among older adults. The absolute count of the excess deaths is affected by the population size.
Dr Samira Asma, assistant director general for data, analytics and delivery at WHO, said, "Measurement of excess mortality is an essential component to understand the impact of the pandemic.
"Shifts in mortality trends provide decision-makers information to guide policies to reduce mortality and effectively prevent future crises. Because of limited investments in data systems in many countries, the true extent of excess mortality often remains hidden."
The methods were developed by the WHO's Technical Advisory Group for Covid-19 Mortality Assessment, co-chaired by Professor Debbie Bradshaw and Dr Kevin McCormack with extensive support from Professor Jon Wakefield at the University of Washington.
The methods rely on a statistical model derived using information from countries with adequate data; the model is used to generate estimates for countries with little or no data available. The methods and estimates will continue to be updated as additional data become available and in consultation with countries, the WHO added.