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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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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 8: Karnataka on Wednesday reported the biggest single-day spike of 2,062 coronavirus cases and a record 54 fatalities, taking the total number of infections to 28,877 and the death count to 470, the health department said.

778 COVID-19 patients were also discharged after recovery in the state.

Out of the fresh cases reported today, 1,148 cases were reported from Bengaluru alone with 22 deaths.

The previous biggest single-day spike was recorded on July 5 with 1,925 cases.

As of July 8 evening, cumulatively 28,877 COVID-19 positive cases have been confirmed in the state, which includes 470 deaths and 11,876 discharges, the health department said in its bulletin.

It said out of 16,527 active cases, 16,075 patients are in isolation at designated hospitals and stable, while 452 are in ICU.

The dead include 22 from Bengaluru urban, Dharwad seven, Ballari four, three each from Hassan and Raichur, two each from Ramanagara, Chikkaballapura, Vijayapura, Tumakuru, Mysuru, and one each from Bidar, Dakshina Kannada, Kalaburagi, Chikkamagaluru and Bengaluru rural.

Among the districts where the new cases were reported, Bengaluru urban accounted for 1,148 cases, followed by Dakshina Kannada 183, Dharwad 89, Kalaburagi 66, fifty nine each from Ballari and Mysuru, Bengaluru rural 37, Ramanagara 34, Chikkaballapura 32, 31 each from Udupi and Haveri, Bidar 29, Belagavi 27, Hassan 26, and 24 each from Bagalkote and Tumakuru.

While Chikkamagaluru reported 23 cases, it was 20 in Mandya, Uttara Kannada 19, Davangere 18, 17 each from Raichur and Shivamogga, Kolar 16, 11 each from Yadgir and Koppal, Gadag five, Vijayapura four, and Chitradurga two.

Bengaluru urban district tops the list of positive cases, with 12,509 infections, followed by Kalaburagi 1,816 and Dakshina Kannada 1,534.

Among discharges, Bengaluru urban tops the list with 2,228 discharges, followed by Kalabuagi 1,351 and Udupi 1,178.

A total of 7,59,181 samples were tested so far, out of which 19,134 were tested on Wednesday alone.

According to the bulletin, so far 7,11,319 samples have been reported as negative, and out of them 16,503 were reported negative today.