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Feb 22: A 20-year-old Chinese woman from Wuhan, the epicentre of the coronavirus outbreak, travelled 400 miles(675 km) north to Anyang where she infected five relatives, without ever showing signs of infection, Chinese scientists reported on Friday, offering new evidence that the virus can be spread asymptomatically.

The case study, published in the Journal of the American Medical Association, offered clues about how the coronavirus is spreading, and suggested why it may be difficult to stop.

"Scientists have been asking if you can have this infection and not be ill? The answer is apparently, yes," said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, who was not involved in the study.

China has reported a total of 75,567 cases of the virus known as COVID-19 to the World Health Organization (WHO) including 2,239 deaths, and the virus has already spread to 26 countries and territories outside of mainland China.

Researchers have reported sporadic accounts of individuals without any symptoms spreading the virus. What's different in this study is that it offers a natural lab experiment of sorts, Schaffner said.

"You had this patient from Wuhan where the virus is, travelling to where the virus wasn't. She remained asymptomatic and infected a bunch of family members and you had a group of physicians who immediately seized on the moment and tested everyone."

According to the report by Dr Meiyun Wang of the People's Hospital of Zhengzhou University and colleagues, the woman travelled from Wuhan to Anyang on Jan. 10 and visited several relatives. When they started getting sick, doctors isolated the woman and tested her for coronavirus. Initially, the young woman tested negative for the virus, but a follow-up test was positive.

All five of her relatives developed COVID-19 pneumonia, but as of Feb. 11, the young woman still had not developed any symptoms, her chest CT remained normal and she had no fever, stomach or respiratory symptoms, such as cough or sore throat.

Scientists in the study said if the findings are replicated, "the prevention of COVID-19 infection could prove challenging."

Key questions now, Schaffner said, are how often does this kind of transmission occur and when during the asymptomatic period does a person test positive for the virus.

India continues to remain ranked 43rd on an annual World Competitiveness Index compiled by Institute for Management Development (IMD) with some traditional weaknesses like poor infrastructure and insufficient education investment keeping its ranking low, the international business school said on Tuesday.

Singapore has retained its top position on the 63-nation list.

Denmark has moved up to the second position (from 8th last year), Switzerland has gained one place to rank 3rd, the Netherlands has retained its 4th place and Hong Kong has slipped to the fifth place (from 2nd in 2019).

The US has moved down to 10th place (from 3rd last year), while China has also slipped from 14th to 20th place. Among the BRICS nations, India is ranked second after China, followed by Russia (50th), Brazil (56th) and South Africa (59th).

India was ranked 41st on the IMD World Competitiveness Ranking, being produced by the business school based in Switzerland and Singapore every year since 1989, but had slipped to 45th in 2017 before improving to 44th in 2018 and then to 43rd in 2019.

While its overall position has remained unchanged in the 2020 list, it has recorded improvements in areas like long-term employment growth, current account balance, high-tech exports, foreign currency reserves, public expenditure on education, political stability and overall productivity, the IMD said.

However, it has moved down in areas like exchange rate stability, real GDP growth, competition legislation and taxes.

Arturo Bris, Head of Competitiveness Center at IMD Business School, said India continues to struggle on the list and the recent country rating downgrade by Moody’s reflects the uncertainties regarding the economy’s future.

"In our ranking this year, we again emphasize the traditional weaknesses of India -- poor infrastructure, an important deficit in education investment, and a health system that does not reach everybody. For India to follow the path of China, it must stress its intangible infrastructure," Bris said.

"In a less global world, with China, USA, and Europe looking inwards, currencies like the rupee (and the Brazilian real for instance) are going to suffer and display high volatilities.

"Moody’s has threatened the country with a downgrade to junk and that would put India in a terrible position to attract foreign capital. So the urgency for the government should be to fix the short-term problems—and this requires to improve the credibility of the government itself," Bris added.

With the exception of Singapore, the Philippines, Taiwan and the Korean Republic, most Asian economies dropped in rankings this year, the IMD said.

The reason for the Asian economies’ less stellar performance as a region, this year is partly the result of the trade frictions between China and the US, particularly because these economies are highly dependent on trade with China.

About Singapore, which moved to the top rank last year, the IMD said its position is largely driven by the relative ease of setting up business, availability of skilled labour and its cutting-edge technological infrastructure.

The IMD said the impact of COVID-19 on the competitiveness ranking has partially been captured by executives’ opinions about the effectiveness of the different health systems.

In the ASEAN countries included in the survey, only Singapore and Thailand have a positive performance in the effectiveness of the health infrastructure.

London, May 20: The current physical distancing guidelines of 6 feet may be insufficient to prevent COVID-19 transmission, according to a study which says a mild cough in low wind speeds can propel saliva droplets by as much as 18 feet.

Researchers, including those from the University of Nicosia in Cyprus, said a good baseline for studying the airborne transmission of viruses, like the one behind the COVID-19 pandemic, is a deeper understanding of how particles travel through the air when people cough.

In the study, published in the journal Physics of Fluids, they said even with a slight breeze of about four kilometres per hour (kph), saliva travels 18 feet in 5 seconds.

"The droplet cloud will affect both adults and children of different heights," said study co-author Dimitris Drikakis from the University of Nicosia.

According to the scientists, shorter adults and children could be at higher risk if they are located within the trajectory of the saliva droplets.

They said saliva is a complex fluid, which travels suspended in a bulk of surrounding air released by a cough, adding that many factors affect how saliva droplets travel in the air.

These factors, the study noted, include the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.

In the study, the scientists created a computer simulation to examine the state of every saliva droplet moving through the air in front of a coughing person.

The model considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapour and evaporate, along with a grid representing the space in front of a coughing person.

Each grid, the scientists said, holds information about variables like pressure, fluid velocity, temperature, droplet mass, and droplet position.

The study analysed the fates of nearly 1,008 simulated saliva droplets, and solved as many as 3.7 million equations.

"The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves," explained Talib Dbouk, another co-author of the study.

However, the researchers added that further studies are needed to determine the effect of ground surface temperature on the behaviour of saliva in air.

They also believe that indoor environments, especially ones with air conditioning, may significantly affect the particle movement through air.

This work is important since it concerns safety distance guidelines, and advances the understanding of the transmission of airborne diseases, Drikakis said.