‘Virus can travel nearly 20 ft as social distancing norms of 6 ft insufficient’ Most viruses, other germs do not spread EASILY ON FLIGHTS: CDC
COVID-19 CAN SPREAD UP TO 3 TIMES FURTHER IN COLD, HUMID WEATHER
LOS ANGELES: Scientists have modelled the spread of infectious droplets from coughing, sneezing, and breathing under different atmospheric conditions, and found that the novel Coronavirus can spread up to three times further in cold and humid weather.
According to the researchers, including those from the University of California (UC) Santa Barbara in the US, droplets carrying the virus can travel up to 20 feet, making the current social distancing norms of six feet insufficient to contain its spread.
Based on previous research, they said as many as 40,000 respiratory droplets can be generated by sneezing, coughing, and even normal talking, with initial speeds ranging from a few metres per second to more than a hundred meters per second.
From these past studies, the scientists said both the aerodynamics of the droplets, and their heat and mass exchange process with the environment can determine the effectiveness of virus propagation.
In the yet-to-be peer reviewed study, published as a preprint in medrxiv, the scientists used a comprehensive mathematical model to explore the evaporation, heat transfer, and projectile motion of respiratory droplets under different temperature, humidity, and ventilation conditions.
They found that the transmission pathway of COVID-19 through respiratory droplets is divided into short-range drop
let contacts, and long-range aerosol exposure.
"While large droplets usually settle onto a surface within a limited distance due to gravity, smaller droplets evaporate rapidly to form aerosol particles that are able to carry the virus and float in air for hours," the scientists wrote in the study.
According to their analysis, the effect of weather conditions on this pathway is not the same every time. Low temperature and high humidity facilitates droplet contact transmission, while high temperature and
low humidity promotes small aerosol-particle formation, the researchers said.
"Our model suggests that the 6 feet of social distance recommended by the Center for Disease Control and Prevention (CDC) may be insufficient in certain environmental conditions, as the droplet spreading distance can be as long as 6 metres (19.7 feet) in cold and humid weather," the scientists wrote in the study.
The researchers warned that the current pandemic may not stop in the summer of the northern hemisphere without proper intervention since there is an increasing chance of aerosol transmission in these parts of the world.
The study noted that in hot and dry weather, respiratory droplets more easily evaporate into aerosol particles capable of
long-range transmission. It said these small particles can infiltrate deeply into the lungs, and have a longer suspension time in these conditions. According to the researchers, many public spaces implement air-conditioning systems that can still operate at temperature and humidity set points that favour droplet transport, preventing
long range transmission. While ventilation can effectively dilute the accumulation of infectious aerosol particles, improper design of these systems may void the effort of social distancing by enabling the aerosol-size particles to travel further, they said.
However, wearing a face mask can effectively lower the chance of transmission via aerosol particles, the scientists said, adding that the risk of infection from large droplets can be mitigated by practising social distancing.
The infection range of large droplets, they said, is limited to a relatively short distance, since they are more sensitive to gravity and can settle on a surface before drying.
If these droplets happen to land on the upper body of another person, viruses can easily enter them by facetouching and eye-rubbing, which can be prevented by practising social distancing, the researchers explained.
However, citing the limitations of the study, the scientists said the survivability of the virus itself under different weather conditions remains unknown.
WASHINGTON DC: Most viruses and other germs do not spread easily on flights, the US Center for Disease Control and Prevention has said in its COVID-19 guidelines which do not recommend following social distancing between two passengers inside a plane or keeping the middle seat unoccupied.
As a result of Coronavirus pandemic, air traffic inside the US has come to a near halt. Air traffic is said to be down to about 90 per cent. For all travellers coming from overseas, the Center for Disease Control and Prevention (CDC) has recommended 14 days quarantine.
"Most viruses and other germs do not spread easily on flights because of how air circulates and is filtered on airplanes," the CDC has said in its set of COVID-19 guidelines for air travellers.
However, it noted that the air travellers were not riskfree specially in the time of the Coronavirus pandemic and recommended Americans to avoid travel as far as possible.
"Air travel requires spending time in security lines and airport terminals, which can bring you in close contact with other people and frequently touched surfaces," it said.
"Social distancing is difficult on crowded flights, and you may have to sit near others (within six feet), sometimes for hours. This may increase your risk for exposure to the virus that causes COVID-19," the CDC said.
But instead of recommended social distancing inside commercial planes, the CDC has advised a series of preventive and hygienic measures to be taken by the airlines pilot and crew to prevent the spread of Coronavirus.
The US Department of Transportation and Federal Aviation Administration in its
latest safety alerts for operators on May 11 said that air carriers and crews conducting flight operations having a nexus to the US, including both domestic and foreign air carriers, should follow CDC'S occupational health and safety guidance. The CDC issued its guidelines in first guidelines for the airlines and airline crew on March and again in May.
The CDC, which has issued an exhaustive social guide
line measures in various sections, is silent on keeping the middle seat of a plane unoccupied so as to maintain the six feet distance between two passengers.