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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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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

Thiruvananthapuram, Feb 17: Out of the total 418 samples of suspect coronavirus cases sent for testing to National Institute of Virology from Kerala, 405 have come out as negative, while the results for the rest, barring three, are awaited.

"Out of three persons in whom the disease was confirmed, two persons have been discharged. One person is stable and the repeat sample results are awaited," according to a release by the Health and Family Welfare Department of the Kerala government.

The release added that till Sunday a total of 2,276 people have been placed under surveillance, "out of which 2262 are under home isolation and 14 are admitted in designated isolation facilities."

The health condition of all symptomatic people under isolation is stable, according to the release.

The release added that the Ministry of Health and Family Welfare (Centre) has informed the Kerala government that 115 people belonging to Kerala are currently in quarantine in two camps in Delhi.

These 115 people have been tested and found negative for coronavirus and they will be allowed to travel back to Kerala on Monday evening.

The people have been requested to remain in home isolation upon their return.