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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.

Tehran, Mar 10: Twenty-seven people have died from methanol poisoning in Iran after rumours that drinking alcohol can help cure the novel coronavirus infection, state news agency IRNA reported on Monday. The outbreak of the virus in Islamic republic is one of the deadliest outside of China, where the disease originated.

Twenty have died in the southwestern province of Khuzestan and seven in the northern region of Alborz after consuming bootleg alcohol, IRNA said.

Drinking alcohol is banned in Iran for everyone except some non-Muslim religious minorities. Local media regularly report on lethal cases of poisoning caused by bootleg liquor.

A spokesman for Jundishapur medical university in Ahvaz, the capital of Khuzestan, said 218 people had been hospitalised there after being poisoned.

The poisonings were caused by "rumours that drinking alcohol can be effective in treating coronavirus," Ali Ehsanpour said.

The deputy prosecutor of Alborz, Mohammad Aghayari, told IRNA the dead had drunk methanol after being "misled by content online, thinking they were fighting coronavirus and curing it." If ingested in large quantities, methanol can cause blindness, liver damage and death.

Iran has been scrambling to contain the spread of the COVID-19 illness which has hit all of the country's 31 provinces, killing 237 people and infecting 7,161.

According to IRNA, 16 out of 69 confirmed cases have died of coronavirus infection in Khuzestan as of Sunday.