JOIN USAirline study shows even Covid-19 asymptomatic patients can spread virus
Asymptomatic Covid-19 patients have the ability to transmit the disease to other people through the contamination of surfaces, a new study on airline passengers has found.
The discovery was made after Korean scientists led by Dr Sung Hwan Bae enrolled 310 passengers flying on a special repatriation flight on March 31 from Milan to South Korea. Eleven of the symptomatic passengers were not permitted to board and the remaining 299 were embarked after each was supplied with an N95 mask.
In addition, the 299 people had kept two metres distance from each other during pre-boarding and all of the passengers wore the masks during the flight except during mealtimes in the course of the 11-hour flight.
Upon arrival in South Korea, the passengers were subject to 14 days of quarantine at a government centre, during which they were completely isolated from each other.
According to the study, which is due to be published in the peer-reviewed US Centres for Disease Control (CDC) journal Emerging Infectious Diseases this November, it was only when government health officers started testing the passengers on their first day of quarantine on April 1, using RT-PCR kits that something interesting was found: six passengers who had no symptoms of the disease whatsoever tested positive.
When an additional round of testing was conducted on the last day of quarantine on April 15, another passenger, a 28-year-old woman was also found to be positive for the disease after having previously tested negative.
The individual told officials that she had worn her N95 mask throughout the flight, except when she had used a toilet, which had also been shared by other passengers sitting nearby, including one of the asymptomatic passengers.
“She was seated three rows away from the asymptomatic patient. Given that she did not go outside and had self-quarantined for three weeks alone at her home in Italy before the flight and did not use public transportation to get to the airport, it is highly likely that her infection was transmitted in the flight via indirect contact with an asymptomatic patient. She reported coughing, rhinorrhea, and myalgia on quarantine day 8 and was transferred to a hospital on quarantine day 14,” scientists wrote.
The remaining 292 passengers were released from quarantine on day 15. All 10 crew members of the passenger jet and eight medical staff involved in monitoring the passengers who had also been quarantined for 14 days tested negative and were discharged.
Indian Scenario
In the case of India, it is not yet known to what extent infected air travellers were exposed to the disease in-flight. As of July 21, when the Karnataka government stopped sharing patient histories, the state had 586 confirmed cases among international flyers among the state’s overall total of 71,069 Covid-19 patients.
There is no clarity from the government about how many of these people were infected in-flight. In late May, however, DH investigated seven asymptomatic Covid-positive fliers who had returned to Bengaluru on the night of May 22, among 510 repatriated passengers from Doha, Male, Kuala Lumpur and Jakarta.
These positive cases were discovered after their swabs were collected while at a quarantined hotel just before they were discharged. By when the test results came back as positive, many had already been sent home.
One of the passengers was Pradeep (name changed), 35, a resident of Kolar District. Speaking to DH, he was isolated at a government quarantine hotel in Yeshwanthpur, Bengaluru.
“Following my release on May 29, I returned home to Kolar. On the afternoon of May 31, I was told by officials that I had tested positive,” Pradeep said. By that time, Pradeep’s elderly parents, aged 62 and 72, plus a 21-year-old niece had been exposed.
Stringent Global Regulations Needed
The study findings, meantime, prompted the Korean scientists to write that “further attention is warranted to reduce the transmission of Covid-19 on aircraft. Our results suggest that stringent global regulations for the prevention of Covid-19 transmission on aircraft can prevent public health emergencies.”
A second experiment involving another repatriation flight of 205 passengers from Milan to Korea on April 3, found three asymptomatic passengers who likely infected one other passenger who had tested negative on day one of quarantine in Korea but subsequently tested positive on day 14.