Roundup: COVID-19 Shutdowns Prevented 60 Million Infections; Droplets on Surfaces; and Latest on Asymptomatic Spread

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June 12, 2020


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Lockdowns, Social-Distancing Policies Prevented Millions of Additional COVID-19 Cases, New Study Finds

Policies involving lockdowns, sheltering-in-place and social distancing helped prevent millions of additional COVID-19 infections in the United States and other nations, a new study published this week has found.

Researchers from the University of California at Berkeley reviewed more than 1,700 local, regional and national policies, including restrictions on travel, the cancellation of events and religious gatherings, and the closing of schools, offices and retail businesses — beginning in early April. They compared the growth rate of infections within hundreds of regions before and after each of these policies was implemented locally, using statistical formulas more commonly used to measure economic growth rates.

“Our results suggest that ongoing anti-contagion policies have already substantially reduced the number of COVID-19 infections observed in the world today,” researchers concluded. The study’s estimates suggest there would have been 4.8 million more confirmed cases (which would have resulted in 60 million more total infections) in the U.S. had this nation never enacted any anti-contagion policies, including sheltering-in-place and social-distancing orders.

Researchers came up with similar estimates for other nations. If it were not for “anti-contagion policies,” there would be roughly 37 million more cumulative confirmed cases (corresponding to 285 million more total infections) in China; 11.5 million more confirmed cases in South Korea (38 million total infections); 2.1 million more confirmed cases in Italy (49 million total infections); 5 million more confirmed cases in Iran (54 million total infections); and 1.4 million more confirmed cases in France (45 million total infections).

By using lockdowns and other anti-coronavirus policies, these six countries overall prevented or delayed as many as 62 million confirmed coronavirus cases, which in turn helped avert roughly 530 million total infections, researchers estimate.


How Long Coronavirus Stays on Surfaces Linked to Temperature and Humidity, Study Says

The amount of time COVID-19 droplets last on surfaces may be connected to surrounding temperature and humidity — and the type of surface infected, researchers have found.

According to study published in Physics of Fluids journal, the likelihood of COVID-19 surviving on a surface increases by about 5 times in a humid environment, compared to a dry one. In another finding, researchers found that higher temperatures can kill the virus more quickly.

The coronavirus most commonly spreads through droplets in the air when an infected person coughs, sneezes, or talks loudly. But some of these droplets can settle on surfaces, which prompted researchers to determine the length of time it takes the droplets to evaporate. The longer the evaporation, the more likely it is that the droplets could infect someone new who comes in contact with the infected surface.

The finding that higher temperatures and lower humidity dry out droplets faster could partially explain why the coronavirus took hold in some geographic areas more than others. The researchers reviewed droplets’ average drying time in six cities, with different temperatures and humidity levels — Chicago, Los Angeles, Miami, New York City, Singapore and Sydney. “A longer drying time correlated with a larger growth rate of the pandemic,” according to Raneesh Bhardwaj, one of the study’s co-authors.

The study also indicates that hydrophilic (moisture-friendly) surfaces, such as smartphone screens and wood, should be cleaned more often than glass and steel surfaces. Droplets evaporate faster on glass and steel, the study states.


Asymptomatic Spread of COVID-19 Still a Concern, Despite ‘Rare’ Comment from WHO Official

The World Health Organization clarified this week that public health officials and scientists have not determined yet how frequently people with no symptoms spread COVID-19 to others. A day earlier, a top WHO official suggested such “asymptomatic” cases are “rare,” citing a few inconclusive studies.

Maria Van Kerkhove, M.D., chief of the WHO’s emerging diseases and zoonosis unit, clarified her initial remark, saying that actual rates of asymptomatic transmission aren’t yet known.

“The majority of transmission that we know about is that people who have symptoms transmit the virus to other people through infectious droplets,” Dr. Van Kerkhove said. “But there are a subset of people who don’t develop symptoms, and to truly understand how many people don’t have symptoms, we don’t actually have that answer yet.”

Last month, the U.S. Centers for Disease Control and Prevention (CDC) estimated that as many as 35 percent of coronavirus patients don’t show symptoms. A report from the CDC in April focused on the “potential for presymptomatic transmission” as a major factor in practicing social distancing.

Some people infected by the coronavirus, especially young or otherwise healthy individuals, never develop symptoms, including the commonly cited fever, cough and difficulty breathing. Many only show very mild symptoms. Other people may develop symptoms several days after being infected.

Early reports on the COVID-19 outbreak in the U.S. and in other countries indicated that the virus could widely spread from person-to-person, even if the carrier didn’t show symptoms. WHO officials now say that asymptomatic spread does happen — but it is probably not the primary way the virus is transmitted.

“We are constantly looking at this data and we’re trying to get more information from countries to truly answer this question,” said Dr. Kerkhove.

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