social distancing study, COVID-19
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A new study shows travelling from the home is associated with significantly higher likelihood of contracting COVID-19, while strict social distancing prevents infection

Researchers from the Johns Hopkins Bloomberg School of Public Health say that similar studies could be used to predict local trends in infectious outbreaks.

The study is among one of the first large scale evaluations into social distancing and behaviour associated with COVID-19. It is based on individual-level survey data, as opposed to aggregated data from sources such as mobile apps.

Researchers suggest that using public transportation, visiting a place of worship, or otherwise traveling from the home is associated with a significantly higher likelihood of testing positive with the coronavirus SARS-CoV-2, while adhering to strict social distancing rules is associated with a markedly lower likelihood.

The team surveyed a random sample of more than 1,000 people in the state of Maryland in late June, asking about their social distancing practices, use of public transportation, infection history, and other COVID-19-relevant behaviours.

A tenth less likely to risk infection with social distancing

The results, which were published in Clinical Infectious Diseases, found that those reporting frequent public transport use were more than four times as likely to report a history of testing positive for COVID-19 infection, while those who reported practising strict outdoor social distancing were just a tenth as likely to report ever being COVID-19 positive.

Senior author and Associate Professor of Medicine at Johns Hopkins School Medicine, Sunil Solomon, said: “Our findings support the idea that if you’re going out, you should practice social distancing to the extent possible because it does seem strongly associated with a lower chance of getting infected.

“Studies like this are also relatively easy to do, so we think they have the potential to be useful tools for identification of places or population subgroups with higher vulnerability.”

COVID-19 has infected nearly 27 million people globally. In the absence of a vaccine, public health authorities have emphasized practices such as staying at home, wearing masks and maintaining social distancing while in public. Yet there hasn’t been a good way to monitor whether, and among which groups, such practices are being followed.

The 1,030 people included in the study were all living in Maryland, which has logged more than 113,000 confirmed COVID-19 cases and nearly 3,700 confirmed deaths, according to the Maryland Department of Health.

The researchers asked the participants questions about recent travel outside the home, their use of masks, social distancing and related practices, and any confirmed COVID-19 infection.

The results showed that 55 (5.3%) of the 1,030 participants had tested positive for COVID-19 infection at any time, while 18 (1.7%) reported testing positive in the two weeks before they were surveyed.

The risk of using public transport

The researchers found that spending more time in public places was strongly associated with having a history of COVID-19 infection. For example, an infection history was about 4.3 times more common among participants who stated that they had used public transportation more than three times in the prior two weeks, compared to participants who stated they had never used public transportation in the two-week period.

An infection history also was 16 times more common among those who reported having visited a place of worship three or more times in the prior two weeks, compared to those who reported visiting no place of worship during the period.

Conversely, the study showed those who reported practicing social distancing outdoors ‘always’ were only 10% as likely to have a COVID-19 infection history, compared to those who reported ‘never’ practicing social distancing.

An initial, relatively simple analysis linked many other variables to infection history, including being Black or Hispanic. But a more sophisticated, analysis suggested these COVID-19 infections were more to do with differences in movement and social distancing.

First author, Steven Clipman, commented: “When we adjusted for other variables such as social distancing practices, a lot of those simple associations went away, which provides evidence that social distancing is an effective measure for reducing SARS-CoV-2 transmission,”

Protecting the vulnerable by practicing social distancing

The data from the study indicated a greater adoption of social distancing practices among some groups who are especially vulnerable to COVID-19 illness, suggesting that they were relatively aware of their vulnerability.

For example, 81% of over-65 participants reported always practicing social distancing at outdoor activities, while only 58% of 18-24-year olds did so.

The results are consistent with the general public health message that mask-wearing, social distancing, and limiting travel whenever possible reduce COVID-19 transmission.

The researchers suggest, to further improve the prevention of COVID-19 transmission, employing similarly rapid surveys of targeted groups, could also help predict where and among which groups infectious diseases will spread most quickly.

Solomon and his team are now conducting similar surveys in other states and are studying the surveys’ potential as predictive epidemiological tools.


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