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Mangaluru, Jul 16: Streets in Mangaluru wore a deserted look as the city woke up to the first morning of the seven-day lockdown on Thursday.

The lockdown is being observed after the state government announced it as a necessary step to combat the spread of COVID-19.

The week-long total shutdown came into effect in the Karnataka's Dakshina Kannada district from 8 pm on July 15 till 5 am on July 22.

The state government allowed relaxation between 8am to 11 am for purchasing of essential commodities. A slight rush was observed during the hours of the relaxation.

Karnataka has so far reported 47,253 positive COVID-19 cases, including 27,859 active cases and 18,466 recoveries.

So far, 928 people have lost their lives due to the infectious virus in the state.

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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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, May 28: As many as 115 new coronavirus cases were reported in Karnataka on Thursday taking the infection count to 2,533, Karnataka Minister S Suresh said.

The total coronavirus cases include 834 discharges, 1,650 active cases, 47 deaths so far due to the disease and two deaths due non-COVID causes, Suresh Kumar, who is minister for primary and secondary education, said during the daily COVID-19 briefing.

According to him, 29 cases were reported in Udupi on Thursday, followed by 24 in Dakshina Kannada district, 13 in Hassan, 12 in Bidar, nine in Bengaluru Urban, seven in Yadagiri, six in Chitradurga, five in Kalaburagi, four in Haveri, three in Chikkamagaluru, two in Vijayapura and one in Raichur.

The minister said among the new cases, 95 are inter-state passengers and two international passengers.

According to the health department, 84 infected people have returned from Maharashtra and eight from Tamil Nadu.

Among those discharged today, 13 are in Davangere, 12 in Dakshina Kannada, nine each in Yadagiri and Vijayapura, five in Gadag, three in Belagavi, one each in Mysuru and Bagalkote.

Two are severe acute respiratory infection cases.

There were, however, no coronavirus related deaths in the state today, the minister said.

Kumar said the government has issued another circular making changes in the quarantine rules.

"A person who has completed seven days of institutional quarantine and is asymptomatic can be permitted for home quarantine without a COVID test, subject to undergoing medical check-up," the minister said.

According to the circular, all elderly people of above 60 years of age and those with comorbidities such as diabetes, hypertension, asthma, heart ailment and renal diseases, are required to be clinically evaluated diligently prior to shifting them to home quarantine.

Such people will be under mandatory home quarantine for seven days, the circular read.