E-Paper
Covid-19 transmission on flight from New Delhi, in hotel corridor, finds New Zealand study
The researchers identified a multibranched chain of transmission of coronavirus, including a probable case of aerosol transmission without direct person-to-person contact.
The transmission of coronavirus occurred on an international flight, in a hotel corridor, and then to household contacts despite the efforts taken by authorities to isolate and quarantine patients, New Zealand researchers have found. In a study published in the journal Emerging Infectious Diseases, the researchers identified a multibranched chain of transmission of coronavirus among nine patients, including a probable case of aerosol transmission without direct person-to-person contact.
A cohort of 149 repatriated New Zealand citizens or permanent residents, without any pre-departure testing, travelled from New Delhi to Christchurch on August 26, 2020, on a Boeing 747 chartered flight via Nadi, Fiji, the researchers reported. While several passengers remained in Fiji, others arrived in Christchurch and were put under managed isolation and quarantine (MIQ) for 14 days.
Out of all the passengers who arrived in Christchurch on the chartered flight, eight showed positive results for coronavirus disease (Covid-19). Three of the case-patients were shown to be genomically linked and have been denoted in the study as case-patients A, B, and C. During the first flight from New Delhi to Nadi, with around 35% occupancy, as per the study, all passengers were evenly spaced throughout the aircraft and case-patients A, B, and C sat within two rows of each other.
Patients A and B tested positive for Covid-19 on August 30, and patient C experienced symptoms on September 6 and tested positive on September 8. The researchers noted that the timing of patient C experiencing symptoms was consistent with transmission by patient A or B during the flight from India to New Zealand.
“Case-patients A or B might have been infected during or before the flight from a common source...the passengers in question did not travel together and did not know each other,” they wrote, highlighting that infection prevention measures were followed by the flight crew and passengers were required to wear facemasks for the duration of the flight.
The researchers then found evidence of transmission in the MIQ facility, which was a repurposed commercial hotel and each room with its own bathroom and no balconies. Patient C tested positive on day 12 of the mandatory quarantine period and was relocated to the isolation section of the facility.
Before patient C’s relocation, an adult and infant child, both of whom had returned from India on the same flight, were quarantined in the adjacent room. The adult and the child completed their 14-day quarantine and tested negative for Covid-19 twice. However, the duo, denoted in the study as case-patients D and E, later showed positive results for SARS-CoV-2 while in the community.
“We consider that these 2 case-patients were infected while in MIQ,” the researcher said.
According to the study, the researchers reviewed closed-circuit television footages between the arrival of patients C, D, and E and the transfer of patient C to the isolation section. The researchers said that there were no instances where the 3 persons were outside of their rooms at the same time.
However, during the routine testing within the doorway of hotel rooms on day 12, there was a 50-second window between closing the door to the room of case-patient C and opening the door to the room of case-patients D and E, said the researchers.
“Therefore, we hypothesized that suspended aerosol particles were the probable mode of transmission in this instance, and that the enclosed and unventilated space in the hotel corridor probably facilitated this event,” they added.
After the mandatory quarantine and repeated negative results for Covid-19, some of the travellers were flown to Auckland on a chartered flight and met household contacts. Two of those contacts, with no recent history of travel outside New Zealand, became infected. The researchers said that they found a genomic link between coronavirus isolated from all nine case-patients.
“These findings reinforce the need for rigorous border control processes for countries pursuing Covid-19 elimination, as well as real-time integration of genomic and epidemiologic data to inform outbreak investigations,” they wrote.
