Government data shows the reproduction rate of the novel coronavirus has declined over the past few weeks, but experts doubt it, saying the number of Covid-19 tests has been inadequate to come to such conclusions.
The rate, also called the R-naught, dropped to an average of 1.05 by the end of last month from the average of 1.6 in April and 1.17 in May, according to data of the Institute of Epidemiology, Disease Control and Research (IEDCR).
It was recorded further down at 1.03 on July 2 while the highest -- 2.1 -- was registered on April 9, shows the data.
R-naught, also called R0, is a representation of the number of new infections estimated to result from a single case. Lower R-naught score means fewer new cases and higher score means the opposite.
It gives insightful information that helps policymakers decide when to enforce strict lockdowns and when to lift the restrictions, said experts.
The IEDCR said it has been gathering data on R-naught since early April, and it has so far worked on more than 50,000 coronavirus cases and those who came in their contact. The Daily Star has obtained the data.
The development comes amid a continuous surge in Covid-19 infections and deaths in the country. Till yesterday, 159,679 have been found coronavirus positive, and the death toll reached 1,997. The first coronavirus case was reported on March 8.
Talking about the IEDCR data, its Principal Scientific Officer ASM Alamgir said, "The R0 is going down because people are following the health guidelines to some extent."
He, however, admitted that the Covid-19 situation was not under control. "The R0 should have been below 1," he said.
The R0 trend appeared to be similar in neighboring India. According to a recent report of The New Indian Express, the R0 was 1.22 before June 7, but it came down to 1.15 in the week of June 7-14.
It happened despite a rapid and worrying surge in Covid-19 cases in several parts of the country.
Some experts have meanwhile questioned the credibility of the IEDCR data and its ability to depict the real Covid-19 situation.
Prof Be-Nazir Ahmed, former director of communicable disease control at the Directorate General of Health Services (DGHS), said R0 depends on data quality. "I don't know whether the contact tracing was done properly."
Dr Jahidur Rahman, virologist and assistant professor at Shahid Suhrawardy Medical College, said, "We can't be complacent about this data. The R0 is low as the number of tests is also low. The data will be significant only when there will be massive testing."
According to www.worldometers.info, 5,070 out of every one million people in the country have so far been tested, whereas the number is 109,668 in the United States, 92,222 in Italy and 6,913 in India.
The government has managed to test only about one out of every 250 people, which is direly inadequate to get any conclusive picture of the real Covid-19 situation on the ground, said experts.
Asked, ASM Alamgir contested these observations and said, "People have a misconception that we don't do any contact tracing. We certainly do this."
He also claimed that sample size did not matter for getting credible data on R0.
He said the R0 had increased after a two-month-long shutdown, driven by the coronavirus, was relaxed in May. "If you see the data, you will find that the R0 was rising when the shutdown was eased. But then it declined again gradually."
He then pointed out that the virus was spreading mainly by those were not showing any symptoms.
Replying to a query, Alamgir said, "The number of covid-19 cases did not surge suddenly. So, the case numbers will also not fall abruptly."
The lead virologist at the IEDCR hoped that the ongoing zone-wise lockdown would bring good results in the fight against Covid-19 and that the R0 would continue to fall till the end of this month.
He, however, feared it might rise again in August during the Eid-ul-Azha holidays when people's movement is likely to increase.
Meanwhile, Mushtuq Husain, IEDCR consultant and epidemiologist, said, "R0 above one means it is still dangerous. Although the infection rate is decreasing, the number of infected patients is increasing horizontally."
He also said the asymptomatic cases would be at least 10 times higher than those confirmed by laboratory tests.
R0 for Covid-19 in Germany was 0.75 in May, but it rose to 2.88 on June 22, according to the Robert Koch Institute.
In Brazil, the R0 now stands at 1.51, according to the local media.