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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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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, June 22: Even as the covid-19 positive cases are steadily increasing in Karnataka, an expert has claimed that community transmission has begun in Bengaluru and cases could keep rising over the next two months.

“If you look at the natural course of this virus across countries around the world, it is about six months. Now we’re in the fourth month. This will go on for another two months. It also sounds like this is the beginning of the peak. There is also a possibility of the number of cases going up from now on. Even across India, cases are increasing,” says Dr CN Manjunath, director of Sri Jayadeva Institute of Cardiovascular Sciences and Research and State Task Force member.

Besides the increase in number of cases, the virus is advancing silently, stealthily. A lot of people who are testing positive are asymptomatic. In areas like Padarayanapura, Nanjangud and many places in north Karnataka, there have been positive cases who have not had any contact with infected individuals. Some cases recorded in Bengaluru over the last two to three days have not had any contact with Covid-positive people.

Dr Manjunath adds: “We are in community transmission. This will happen because nature is ahead of everything. We have to take all possible precautionary measures at our command. This has to happen. Only then some kind of herd immunity will be developed.”

“We are expanding the guidelines of testing to include a large number of people to be tested. Now, according to the Indian Council for Medical Research (ICMR) guidelines, only symptomatic Influenza like Illness (ILI) or Severe Acute Respiratory Infection (SARI), or a person coming in contact with an infected person are being tested.

But since we have crossed 100 days in Karnataka from the first reported case and we’re getting cases with no travel history or contact with a Covid-positive person, we have to start random testing across the sub-group population. Only then will we understand the burden of the disease and what precautions need to be taken,” he says.