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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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

Bengaluru, Jul 6: Karnataka government has revised quarantine norms according to which those entering the State from other states, including from Maharashtra, shall be placed in 14-days home quarantine.

Until now, the state government had issued that those returning from Maharashtra are to be placed under 7-day institutional quarantine followed by 7-day home quarantine.

A fresh state government order with the subject line "Regulation of movement of persons from other States to Karnataka" reads: "Whereas the State Government vide Order dated June 30, issued unlock 2 guidelines which permit reopening of more activities in a calibrated manner, in areas outside the Containment Zones, and to extend lockdown in Containment Zone upto July 31. The guidelines also permit unrestricted interstate movement of persons and goods adhering to the SOPs/ Guidelines issued by the Department of Health and Family Welfare and Department of Revenue (Disaster Management)".

Whereas, the Department of Health and Family Welfare issued revised SOP for the moment of persons from other State to Karnataka vide document dated June 8, this year, further, quarantine norms were modified vide Orders of even number dated June 15 and June 26.

"The quarantine norms are regularly reviewed and calibrated with the prevailing Unlock 2 guidelines and infusion of technology and community involvement to enforce the strict home quarantine. In light of the above, the quarantine norms issued vide Order dated June 26, has been further modified and is follows--Persons coming from other State to Karnataka, including Maharashtra shall be placed in 14-days Home Quarantine," the order read.

"The other conditions as specified in the Order dated June 15 and aforementioned SOP enclosed issued on June 8 by the Department of Health and Family Welfare shall continue to be in force until further orders," it added.