- WHO recommends at least one meter physical distance
- US Center for Disease Control advises 2 meters physical distance
- The virus will end at a certain distance
- Will reducing distance to 0.75 m result in more infections?
- Physical distance, face mask and face shield increase protection against COVID-19
Physical distancing is an important measure in the list of health protocols to prevent the transmission of the coronavirus disease 2019 (COVID-19).
But what is the safer distance for physical distancing?
The question on what is the specific distance came up in the past few days after public transportation vehicles were allowed to reduce the distance between passengers from the accepted one-meter distance to 0.75 meter. The move would allow public transport to carry more people to work as more businesses had reopened after Metro Manila was placed under general community quarantine (GCQ).
So, how far can the virus travel? Or, how long can one sit in a closed space with a person who may be infected, to get contaminated — even while wearing a face mask and face shield?
“The virus, even if it’s airborne or droplet borne, it will end at a certain distance,” said Pharmaceutical and Healthcare Association of the Philippines (PHAP) President Dr. Beavery Tamesis, in a recent interview with the Manila Bulletin.
He said that keeping a safe distance from other persons is the “most important way of preventing” COVID-19, aside from wearing of face masks and face shield.
Even if government suspended the reduced physical distancing to .75 meter three days after its implementation and returned to the one-meter distance between passengers, it's good to find out what experts recommend to be the perfect physical distance, the way the virus travels, the possible results of reducing physical distancing in pubic transportation.
‘The perfect distance’
There are many recommendations on how far a susceptible host should keep distance from an infected person to avoid getting infected by COVID-19.
The general and accepted distance is at least one meter from another person which is reflected in many websites of health organizations.
In the World Health Organization’s (WHO) guidelines on “Infection prevention and control of epidemic- and pandemic-prone acute respiratory infections in health care,” the organization recommends keeping at least a one-meter distance from another person to prevent possible transmission of viral particles.
“A distance of less than one meter is associated with an increase in the risk of ARI (acute respiratory infections) pathogen transmission,” the WHO added.
A systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses published in The Lancet on June 1, 2020, said: “Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m, and protection was increased as distance was lengthened. Face mask use could result in a large reduction in risk of infection.”
The United States Center for Disease Control and Prevention (CDC), on the other hand, recommends a two-meter or six feet distance between people, particularly in public transport.
“When using public transit, try to keep at least six feet from other passengers or transit operators – for example, when you are waiting at a bus station or selecting seats on a bus or train,” the CDC suggested.
The pros and cons of reducing physical distancing
The Department of Health (DOH) said the reduced distance in public transportation may result in 686 new cases daily in the National Capital Region.
The Healthcare Professionals Alliance Against COVID-19 (HPAAC) said it sees “hundreds of cases increasing” because of the reduction of physical distancing”
Dr. Anna Ong-Lim of HPAAC said “until more reliable information could be obtained,” the government should reconsider reducing physical distancing.
Former special adviser to the National Task Force against COVID-19 Dr. Tony Leachon, citing information from The Lancet, said a one-meter distance can reduce the chance of infection by up to 86 percent, while a two-meter and three-meter distance can reduce infection by 93 percent and 96 percent, respectively.
The former task force adviser also said in a television interview recently that during the 1918 Spanish influenza pandemic, a surge in cases was noted after physical distancing measures were relaxed.
On the other hand, there are others who don’t think the one-meter physical distance is necessary — as long as people wear face masks and face shields.
Two former DOH chiefs, Dr. Manuel Dayrit and Dr. Esperanza Cabral, both backed the implementation of a reduced physical distancing in public transportation.
Dayrit said “it is possible to go below one meter,” as long as other health measures are being followed.
Dra. Cabral thinks the 0.75-meter adjustment will “make no difference.”
“Walang pinagkaiba sa 0.75 meters kasi lumingon ka lang, iusog mo lang ng konti yung pwet mo doon sa jeep, eh abot mo na yung 0.75 meters na yan (A 0.75-meter adjustment will make no difference because that is just like to turning your head in a different direction or slightly moving your position in jeepneys),” Cabral told DZMM Teleradyo in an interview.
DOTr cited a study conducted by the International Union of Railways that showed hat COVID-19 cases in counties where social distancing has been reduced have actually decreased.
One meter, two meters or even three meters — there will be infection when its in a closed space, the environment group Clean Air Philippines Movement Inc. (CAPMI) president Dr. Leo Olarte told CNN Philippines.
“Virus transmission can still happen inside confined spaces like railway trains, regardless of the distance between passengers,” he said.
He said the most important health measure to practice is the use of face mask and face shield.
‘How far does a virus travel?’
Air quality specialist Lidia Morawska and research professor Junji Cao, in their study, said SARS-COV2, the virus which causes COVID-19, is “transmitted through droplets generated when a symptomatic person coughs, sneezes, talks, or exhales.”
According to WHO, virus transmission occurs when droplets are “propelled through the air and deposited on the conjunctivae, mouth, nasal, throat or pharynx mucosa of another person.”
The distance and length of time in which a droplet can travel or remain suspended in the air is affected by many factors, including its size.
WHO said large particles “typically remain suspended in the air for a limited period of time and settle within 1 meter or 3 feet) of the source.”
“Smaller particles evaporate quickly; the resulting dried residues settle from the air slowly, and remain suspended in the air for variable lengths of time,” WHO explained.
Other studies however showed that droplets can travel farther than a one-meter distance.
Professor Lydia Bourouiba in her journal said that whenever a person infected with respiratory illness coughs or sneezes, “a cloud of pathogen-bearing droplets of different sizes” comes out and travels up to seven to eight meters from point of source.”
“Pathogen-bearing droplets of all sizes can travel for almost 7–8 m during sneezes and for more than 2 meters to a maximum of 4.5 meters during coughs,” the study revealed.