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Singapore, Mar 23: Oil prices fell at the open in Asia on Monday after a trillion-dollar Senate proposal to help the coronavirus-hit American economy was defeated and death tolls soared across Europe and the US.

US benchmark West Texas Intermediate initially tumbled more than three percent but then pulled back some ground to trade 1.5 percent lower, at $22 a barrel.

Brent crude, the international benchmark, fell 4.9 percent to $25 a barrel.

Prices have fallen to multi-year lows in recent weeks as lockdowns and travel restrictions to fight the virus hit demand, and top producers Saudi Arabia and Russia engage in a price war.

The latest drop came after a trillion-dollar Senate proposal to rescue the US economy was defeated after receiving zero support from Democrats, and with five Republicans absent from the chamber because of virus-related quarantines.

The bill had proposed funding for American families, thousands of shuttered or suffering businesses and the nation's critically under-equipped hospitals.

Coronavirus deaths soared across Europe and the United States at the weekend despite heightened restrictions.

The death toll from the virus -- which has upended lives and closed businesses and schools across the planet -- surged to more than 14,300 Sunday, according to an AFP tally.

AxiCorp chief markets strategist Stephen Innes said that "total demand devastation" had set it.

"Oil markets collapsed out of the gate this morning as prices react... to stringent containment lockdown measures," he said.

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of the American Medical Association, noted that the the current guidelines issued by the WHO and CDC are based on outdated models from the 1930s of how gas clouds from a cough, sneeze, or exhalation spread.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