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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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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, Jun 5: Karnataka registered its highest single-day spike of more than 500 new COVID-19 cases, taking the total number of infections in the state to 4,835, the health department said on Friday.

The previous biggest single-day spurt was recorded on June 2 with 388 cases.

Of the 515 fresh cases reported, 482 are returnees from other states, mostly (about 471) from neighboring Maharashtra. Udupi district saw a major spike with over 200 cases today and the total tally of the district breaching seven hundred cases mark, to stand at 768.

As of June 5 evening, cumulatively 4,835 COVID-19 positive cases have been confirmed in the state, which includes 57 deaths and 1,688 discharges, the department said in its bulletin.

It said, out of 3,088 active cases, 3,075 patients are in isolation at designated hospitals and are stable, while 13 are in ICU.

On Friday, 83 patients have been discharged.

According to state COVID-19 war room data, out of the total 4,835 cases, 93 per cent (4,488 cases) are asymptomatic and 7 per cent (347) are symptomatic.

The new cases include 471 from Maharashtra, three from Delhi, two each from Andhra Pradesh, Telangana and Haryana, and one from Tamil Nadu.

While one is with international travel history from Indonesia. Remaining cases include- contacts of patients earlier tested positive, those from containment zones, those who travelled from other districts, and the ones whose contact history is still being traced.

Among the districts where new cases were reported, Udupi accounts for 204 cases, followed by 74 from Yadgir, Vijayapura 53, Kalaburagi 42, Bidar 39, Belagavi 36, Mandya 13, Bengaluru Rural 12, Bengaluru Urban 10, Dakshina Kannada 8, Uttara Kannada 7, three each from Hassan, Dharwad and Chikkaballapura, two each from Ramanagara and Haveri, and one each from Davangere, Bagalkote, Ballari and Kolar.

Udupi district tops the list of positive cases, with a total of 768 infections, followed by Kalaburagi 552 and Bengaluru urban 434.

Among discharges, Bengaluru urban still tops the list with total 271 discharges, followed by Davangere 147 and Mandya 146.

A total of 3,60,720 samples were tested so far, out of which 13,627 were tested on Friday alone.

So far 3,49,951 samples have reported as negative, and out of them 12,797 were reported negative on Friday.