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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.

New Delhi, Mar 11: According to the Union health ministry, there are 62 confirmed cases of coronavirus in the country.

The Delhi High Court Wednesday sought the stand of the Centre and the Delhi government on a PIL seeking proper and adequate measures to combat coronavirus.

A bench of Chief Justice D N Patel and Justice C Hari Shankar issued notice to the Ministry of Health and the Delhi government seeking their replies on the public interest litigation (PIL) filed by an advocate.

The petition, by lawyer Triveni Potekar, seeks directions to the Centre and the Delhi government to make available important and relevant information on access to and availability of medical facilities for testing and treatment for the coronavirus disease.

Kolkata, May 20: Cyclone 'Amphan' lay centred about 240 km south of Digha in West Bengal on Wednesday morning as an extremely severe cyclonic storm, the Met department said here.

The intensity near the centre of the storm was 170 to 180 kmph gusting to 200 kmph, the Met said.

'Amphan' is very likely to move north-northeastwards and cross West Bengal-Bangladesh coast between Digha and Hatiya, close to the Sunderbans during the afternoon to evening of Wednesday with a wind speed of 155 to 165 kmph gusting to 185 kmph as a 'very severe cyclonic storm', the Met department said.

West Bengal has evacuated more than three lakh people to safer places as the cyclonic storm 'Amphan' roared towards the coastal areas of the state, officials said.

The Met department, which has issued an "orange message" for West Bengal, warned of extensive damage in Kolkata, Hooghly, Howrah, South and North 24 Parganas and East Midnapore districts.

The Met department has advised that all establishments and markets remain closed in Kolkata and adjoining areas and movement of people be restricted on May 20.

There is likely to be disruption of rail and road link at several places, uprooting of communication and power poles, extensive damage to all types of 'kutcha' houses and some damage to "old badly managed pucca" structures and potential threat from flying objects, the weatherman warned.

There is also likelihood of extensive damage to standing crops, plantations and orchards and blowing down of palm and coconut trees, the Met said.

The weatherman has advised diversion or suspension of rail and road traffic in the districts which are likely to be affected.

The Eastern Railway (ER) has cancelled the departure of Howrah-New Delhi AC Special Express for Wednesday.

The departure of 02301 Howrah-New Delhi AC Special Express on Wednesday and 02302 New Delhi-Howrah AC Special Express on May 21 would remain cancelled, the ER said.

Wind speed along and off the coastal areas of West Bengal will reach 75 to 85 kmph with gusts up to 95 kmph from Wednesday morning along and off districts of North and South 24 Parganas, East and West Midnapore, Kolkata, Howrah and Hooghly, Regional Met director G K Das said.

"It will gradually increase thereafter becoming 110 to 120 kmph gusting to 130 kmph over West Midnapore, Howrah, Hooghly, Kolkata and wind speed of 155 to 165 kmph gusting to 185 kmph over the districts of North and South 24 Parganas and East Midnapore of West Bengal from the afternoon to night of May 20," he said.

Under its impact rainfall will occur in most places over the districts of Gangetic West Bengal on Wednesday, with heavy to very heavy downpour with extremely heavy rain at a few places in Kolkata, Howrah, East Midnapore, North and South 24 Parganas and Hooghly districts, he said.

"Storm surge of 4 to 5 metres above astronomical tide is likely to inundate low lying areas of South and North 24 Parganas and about 3 to 4 metres over low lying areas of East Midnapore district of West Bengal during the time of landfall," he said.

The Indian Navy has dispatched a diving team for providing assistance to the West Bengal government in relief operations, a Defence official said.

The diving team from Vishakhapatnam has brought specialised equipment along with them which can be used for rescue in case of flooding and have been positioned at the Naval Service Selection Board at Diamond Harbour in South 24 Parganas district, the official said.