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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.

Washington, May 19: As the scientists across the world are struggling to develop a vaccine for combating coronavirus, US drugmaker Moderna announced on Monday (local time) that the phase I trial of its Covid-19 vaccine has shown positive early results.

The company is hopeful that it's vaccine could be available to the public as early as January next year. Several firms across the world are in the race to develop a vaccine for the deadly virus which has claimed over 3 lakh lives worldwide.

CNN citing Dr. Tal Zaks, Moderna's chief medical officer reported that "if future studies go well, the company's vaccine could be available to the public as early as January".

"This is absolutely good news and news that we think many have been waiting for for quite some time," Zaks was quoted as saying.

Moderna, based in Cambridge, Massachusetts announced that the vaccine developed neutralising antibodies to the virus at levels reaching or exceeding the levels seen in people who have naturally recovered from Covid-19, reported CNN.

These will be followed by phase 2 trials and phase 3 trials, which Moderna plans to start in July.

President Donald Trump had on Friday said that that the United States will be able to deliver a few hundred million doses of COVID-19 vaccine, under 'Operation Warp Speed', by the end of this year.

"I have very recently seen early data from a clinical trial with a coronavirus vaccine and this data made me feel even more confident that we'll be able to deliver a few hundred million doses of vaccine by the end of 2020 and we will do the best we can," Trump had said at a press conference at the White House on Friday.

The total number of global COVID-19 cases was nearing 9 million, while the deaths have increased to over 467,000, according to the Johns Hopkins University.

By Monday morning, the total number of cases stood at 8,927,195, while the fatalities increased to 467,636, the University's Center for Systems Science and Engineering (CSSE) revealed in its latest update.

With 2,279,306 cases and 119,967 deaths, the US continues with the world's highest number of COVID-19 infections and fatalities, according to the CSSE.

Brazil comes in the second place with 1,083,341 infections and 50,591 deaths.

In terms of cases, Russia ranks third (583,879), and was followed by India (410,461), the UK (305,803), Peru (251,338), Spain (246,272), Chile (242,355), Italy (238,499), Iran (204,952), France (197,008), Germany (191,272), Turkey (187,685), Mexico (180,545), Pakistan (176,617), Saudi Arabia (157,612), Bangladesh (112,306) and Canada (103,078), the CSSE figures showed.

The other countries with over 10,000 deaths are the UK (42,717), Italy (34,634), France (29,643), Spain (28,323), Mexico (21,825) and India (13,254).