After five days of mask mandates, the daily coronavirus growth rate slowed by just under 1 percent, while after 21 days, it slowed by about 2 percent, according to the study, reports Xinhua.

Researchers from the Department of Health Management and Policy at the University of Iowa College of Public Health reported the study result in the journal Health Affairs.

Between April 8 and May 15, governors of 15 US states and the mayor of Washington, DC signed orders to place mask mandates in public. The researchers studied changes in the daily county-level COVID-19 growth rates between March 31 and May 22.

They also projected the number of averted COVID-19 cases with the mandates for face mask use in public by comparing actual cumulative daily cases with daily cases predicted by a model if none of the states had enacted the public face cover mandate at the time they did.

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The model estimates suggested that 230,000-450,000 cases may have been averted by May 22 due to these mandates.

The US is currently the worst coronavirus affected country in the world with 4,717,568 confirmed cases and 155,469 deaths.

Coronavirus cases were first reported in China in December last year. The World Health Organization declared it a pandemic in March.

The race for developing a vaccine is on but it is unclear when it will be available. Health experts suggest maintaining personal hygiene, washing hands regularly with soap and running water or alcohol based substance, wearing masks in public and maintaining physical distance from others as measures to curb the virus’ spread.