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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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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, Mar 4: With details of the Bengaluru links of the Covid-19-positive patient from Hyderabad emerging, state health authorities on Tuesday got down to tracking any infection trail he may have left behind before heading home.

Schools from southeast Bengaluru asked parents to send students with masks and hand sanitizers or keep them at home if they had fever. Medical shops in Bengaluru reported panic buying of masks and hand sanitizers.

Two persons with no symptoms — the Hyderabad man’s flatmate in city, and a colleague — reported at Rajiv Gandhi Institute of Chest Diseases and put under watch at the isolation ward. Their test results are expected on Wednesday.

The authorities tracked down 71 people who had come in contact with the Hyderabad man and put them under surveillance. The 24-year-old techie had travelled to Dubai for work on February 15 and returned to Bengaluru on February 20. He attended work on February 20 and 21 before taking a bus to Hyderabad. His flat has been sealed for sanitizing.

According to Telangana officials, at least 36 of the 88 people who came in contact with the techie are showing some symptoms of Covid-19.

Contrary to reports, the infected person was not tested at the KIA since guidelines don’t say flyers from Dubai must be screened. WHO guidelines say identification of the infected person should not be revealed. However, WhatsApp groups were flooded with messages on where the infected person lived and details of his flatmate.