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Houston, Mar 15: Researchers, studying the novel coronavirus, have found that the time between cases in a chain of transmission is less than a week, and over 10 per cent of patients are infected by someone who has the virus, but does not show symptoms yet, a finding that may help public health officials contain the pandemic.

The study, published in the journal Emerging Infectious Diseases, estimated what's called the serial interval of the coronavirus by measuring the time it takes for symptoms to appear in two people with the virus -- the person who infects another, and the infected second person.

According to the researchers, including those from the University of Texas at Austin, the average serial interval for the novel coronavirus in China was approximately four days.

They said the speed of an epidemic depends on two things -- how many people each case infects, and how long it takes cases to spread.

The first quantity, the scientists said, is called the reproduction number, and the second is the serial interval.

Due to the short serial interval of the disease caused by the coronavirus -- COVID-19 -- they said, emerging outbreaks will grow quickly, and could be difficult to stop.

“Ebola, with a serial interval of several weeks, is much easier to contain than influenza, with a serial interval of only a few days,” said Lauren Ancel Meyers, study co-author from UT Austin.

Meyers explained that public health responders to Ebola outbreaks have much more time to identify and isolate cases before they infect others.

“The data suggest that this coronavirus may spread like the flu. That means we need to move quickly and aggressively to curb the emerging threat,” Meyers added.

In the study, the scientists examined more than 450 infection case reports from 93 cities in China, and found the strongest evidence yet that people without symptoms must be transmitting the virus -- known as pre-symptomatic transmission.

More than one in ten infections were from people who had the virus but did not yet feel sick, the scientists said.

While researchers across the globe had some uncertainty until now about asymptomatic transmission with the coronavirus, the new evidence could provide guidance to public health officials on how to contain the spread of the disease.

“This provides evidence that extensive control measures including isolation, quarantine, school closures, travel restrictions and cancellation of mass gatherings may be warranted,” Meyers said.

The researchers cautioned that asymptomatic transmission makes containment more difficult.

With hundreds of new cases emerging around the world every day, the scientists said, the data may offer a different picture over time.

They said infection case reports are based on people's memories of where they went and whom they had contact with, and if health officials move quickly to isolate patients, that may also skew the data.

“Our findings are corroborated by instances of silent transmission and rising case counts in hundreds of cities worldwide. This tells us that COVID-19 outbreaks can be elusive and require extreme measures,” Meyers said.

Months after the outbreak of COVID-19 in Wuhan city of central China, families of those deceased, who contracted the contagious infection, stood in long queues at funeral homes demanding to receive the cremated ashes of their loved ones.

Now this has spurred questions about the actual tally of COVID-19 related casualties in Wuhan, in a renewed pressure on the Chinese government that is already struggling to control its containment narrative of the pandemic spread.

Chinese media outlet Caixin showed how trucks carrying 2,500 urns with the ashes of the deceased COVID-19 cases were being shipped in a funeral home last week. Another picture published revealed how 3,500 urns were stacked within these funeral homes. It is therefore unclear how many urns have been filled in.

According to media reports, workers at several funeral parlors declined to provide any details as to how many urns were waiting to be collected, saying they either did not know or were not authorised to share the number.

Some families said they had been forced to wait for several hours to pick up the ashes. The photos circulated as mass deaths from the virus spiked in cities across the west, including Milan, Madrid and New York, where hospitals were erecting tents to handle the overflow as global infections soar past 500,000, with 24,000 dead.

According to Chinese government figures, 2,535 people in Wuhan have died of the virus. The announcement that a lockdown in place since January would be lifted came after the country said its tally of new cases had hit zero and stepped up diplomatic outreach to other countries hard hit by the virus, sending some of them medical supplies.

But some in China have been skeptical of the accuracy of the official tally, particularly given Wuhan's overwhelmed medical system, authorities' attempts to cover up the outbreak in its initial stages, and multiple revisions to the way official cases are counted.

Residents on social media have demanded disciplinary action against top Wuhan officials.

Many people who died had Covid-19 symptoms, but weren't tested and excluded from the official case tally, Caixin said. There were also patients who died of other diseases due to a lack of proper treatment when hospitals were overwhelmed dealing with those who had the coronavirus.

There were 56,007 cremations in Wuhan in the fourth quarter of 2019, according to data from the city's civil affairs agency. The number of cremations was 1,583 higher than those in the fourth quarter of 2018 and 2,231 higher than the fourth quarter of 2017.

Two locals in Wuhan who have lost family members to the virus said online that they were informed they had to be accompanied by their employers or officials from neighborhood committees when picking up the urns, likely as a measure against public gatherings.

COVID-19 is affecting 199 countries and territories around the world. Over 664,000 coronavirus cases have been registered globally out of which 30,890 have succumbed to the infection.