What’s The Risk Of Catching Covid-19 On Public Transportation?

September 10, 2020

The chances of contracting COVID-19 on public transport depend largely on where you sit, with those closest to an infected person at highest risk and those further away at relatively low risk, a new study suggests.

The study, which included thousands of passengers on China’s high-speed trains, known as G trains, found that the rate of infection among nearby passengers ranged from nearly 0 percent to about 10 percent, with those who sat closest to an infected person for the longest time being at the highest risk.

“Our study shows that while the risk of spreading COVID-19 on trains increases, a person’s seating position and travel time in relation to an infected person can have a significant impact on whether or not they are infected,” Dr. Shengjie Lai, lead study author and researcher at the University of Southampton in the UK, said in a statement.” The findings suggest that during a COVID-19 outbreak, it is important to reduce passenger density, promote personal hygiene measures, use face masks and possibly perform temperature checks before boarding.”

In fact, other recent studies from around the world suggest that public transportation may pose a relatively low risk of infection when passengers wear masks and adhere to social distance guidelines.

In Paris, for example, public health officials found that of the 386 recent COVID-19 cluster incidents in the city from May to mid-July, none were related to public transportation, according to the New York Times. Similar findings were made in Tokyo and parts of Austria, according to the Times.

In the new study, published July 29 in the journal Clinical Infectious Diseases, researchers analyzed information on passengers who took the G train between mid-December 2019 and late February 2020, which covers the period from before COVID-19 was discovered to the peak of the outbreak in China.

The researchers identified more than 2,300 passengers, called “index patients,” who developed COVID-19 within 14 days of riding the train, and more than 72,000 passengers who sat near those cases – within three rows (width direction) and five columns (length direction) of the index patients.

Overall, 234 of the 72,000 passengers in the vicinity developed COVID-19 infections related to their train ride. That means the average “attack rate” – or the percentage of the overall population that tested positive – was about 0.32 percent.

Those who sat directly next to an infected person had the highest risk of infection, with an average attack rate of 3.5 percent.

For those who sat in the same row, but not necessarily next to an infected person, the average rate of attack was 1.5 percent. The study found that this was about 10 times higher than the attack rate for those who sat a row or two behind an infected person.

The amount of time a person spent travelling also affected their risk – on average, people who travelled with an infected person had an increased attack rate of 0.15 per cent for every hour they travelled, while those who sat next to an infected person had an increased attack rate of 1.3 per cent per hour.

However, people sitting in the same seat after an infected person gets off the train appear to be at low risk of infection. Of the 1,342 people who sat in a seat previously occupied by an infected person, only one later contracted the disease, with an attack rate of 0.075 percent, according to CTV News.

Researchers believe that in order to prevent the spread of COVID-19, passengers should be separated by at least two seats in the same row and limit their travel time to three hours.

“We hope this will help global authorities understand the measures needed to prevent the virus and in turn help reduce its spread,” Study co-author Andy Tatem, a professor of spatial demography and epidemiology at the University of Southampton and director of WorldPop, a collaboration of scientists dedicated to providing data on human population distribution, said.

The authors point out that their study has limitations. For example, according to CTV News, researchers were unable to prove that 234 passengers must have contracted the virus on the train, even though public health officials had determined that this was their most likely source of infection. In addition, the authors said the study had no information on whether passengers were wearing protective gear, such as masks.