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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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

Apr 9: A panel of experts in the Karnataka state has suggested that the ongoing lockdown should be continued in districts identified as Covid-19 hotspots, including Bengaluru, to limit the spread of the pandemic.

IT companies and government offices providing essential services should be allowed to function with 50% staff, according to the committee headed by Narayana Health chairman Dr Devi Shetty, which submitted its report to chief minister BS Yediyurappa on Wednesday.

It has also asked the government to ease restrictions gradually and take adequate care over the next six months to contain the outbreak. The committee urged the government not to permit AC buses and metro services till April 30 and allow private vehicles only on alternate days (even-odd number-wise) for two weeks after April 15.

The government must close schools and colleges till May 31 and allow only inter-state movement of goods transport. The government could allow non-AC shops to open. It has suggested that the ban on inter-state train and flight services should continue.

Education minister S Suresh Kumar, who is the state Covid-19 spokesperson, said the Cabinet, which is meeting on Thursday, may discuss the recommendations and take a view on de-escalation of the lockdown.

Prime Minister Narendra Modi will interact with chief ministers through videoconference on April 11, after which the government will get an idea about the Centre’s thinking, he said.

While some states including Kerala, Maharashtra and Telangana have favoured continuation of the lockdown, Yediyurappa has not taken any stand publicly and has instead been implementing the Centre’s decision.

Six new cases

Karnataka on Wednesday reported six new Covid-19 positive cases, including that of a 65-year-old person in Kalaburagi, who died due to severe acute respiratory infection.

The health authorities have issued a notice to the private hospital -- where the deceased was initially admitted before being taken to a government hospital -- for not reporting the case to the government. The government has locked down the hospital, kept its entire medical team under quarantine, and police have registered a case of criminal negligence against the hospital authorities.

Of the other five positive cases, two had a travel history to Delhi, one had contact with a Dubai returnee and two others had close contacts with infected people.

This takes the total number of positive cases in the state to 181. Five people have died, while 28 have been discharged so far.