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Mangaluru, Mar 28: After a youth from Dakshina Kannada who tested positive for the deadly Covid-19 revealed that he had travelled by a bus, authorities have requested all his fellow passengers to visit their nearest district hospital. 

The 21-year-old man hailing from Belthangady taluk had flown from Dubai to Bengaluru on March 21 and on the same day travelled to Mangaluru by the KSRTC bus bearing registration number KA 19, F3329. 

As he was suffering from fever and cough he was admitted to Puttur government hospital on March 24. He was tested positive for the novel coronavirus on March 27.   

It is not yet know how many passengers were there on board the above mentioned bus which had departed Bengaluru at 4:30 p.m. on March 21. It is believed that most of the passengers who travelled by this bus are residents of Dakshina Kannada. 

Hence, the KSRTC authorities today requested all the passengers who travelled by this bus to visit their nearest district hospital for necessary checkup. The passengers also were urged to quarantine themselves for next couple of weeks.

The current physical distancing guidelines provided by the World Health Organisation (WHO) and by the US Centers for Disease Control and Prevention (CDC) may not be adequate to curb the coronavirus spread, according to a research which says the gas cloud from a cough or sneeze may help virus particles travel up to 8 metres. The research, published in the Journal of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.

Study author, MIT associate professor Lydia Bourouiba, warned that droplets of all sizes can travel 23 to 27 feet, or 7-8 metres, carrying the pathogen.

According to Bourouiba, the current guidelines are based on "arbitrary" assumptions of droplet size, "overly simplified", and "may limit the effectiveness of the proposed interventions" against the deadly pandemic.

 She explained that the old guidelines assume droplets to be one of two categories, small or large, taking short-range semi-ballistic trajectories when a person exhales, coughs, or sneezes.

However based on more recent discoveries, the MIT scientist said, sneezes and coughs are made of a puff cloud that carries ambient air, transporting within it clusters of droplets of a wide range of sizes.

Bourouiba warned that this puff cloud, with ambient air entrapped in it, can offer the droplets moisture and warmth that can prevent it from evaporation in the outer environment.

"The locally moist and warm atmosphere within the turbulent gas cloud allows the contained droplets to evade evaporation for much longer than occurs with isolated droplets," she said.

"Under these conditions, the lifetime of a droplet could be considerably extended by a factor of up to 1000, from a fraction of a second to minutes," the researcher explained in the study.

The MIT scientist, who has researched the dynamics of coughs and sneezes for years, added that these droplets settle along the trajectory of a cough or sneeze contaminating surfaces, with their residues staying suspended in the air for hours.

"Even when maximum containment policies were enforced, the rapid international spread of COVID-19 suggests that using arbitrary droplet size cutoffs may not accurately reflect what actually occurs with respiratory emissions, possibly contributing to the ineffectiveness of some procedures used to limit the spread of respiratory disease," Bourouiba wrote in the study