Introduction
On March 11
th, 2020, the World Health Organization declared coronavirus disease 2019 (COVID-19) a pandemic [
1]. Following this announcement, countries around the world started to evacuate their residents overseas. Koreans were successfully repatriated from several foreign countries where there was a COVID-19 epidemic [
2,
3]. Unlike the previous Chinese and Japanese evacuations, which were short-haul flights, the evacuation of 80 Koreans from Iran was more challenging [
4] because of additional safety precautions (e.g., separating seats, dividing zones, and managing the use of toilets on board the aircraft). The evacuees were moved from Tehran in Iran to Al Maktoum International Airport in Dubai via an Iranian aircraft on March 19
th, 2020. A doctor was dispatched to be in charge of transport quarantine for flights from Tehran to Incheon. To our knowledge, there are no published reports on air transport according to the World Health Organization air transport guidelines, of a large group of potentially infectious individuals [
5].
1. Zoning
The Korean government selected the Boeing 777-200 aircraft as a charter plane to accommodate the number of residents required to be repatriated to Korea. The first-class seats in the front were designated as a clean zone, and the economy seats in the middle and rear were designated as a contaminated zone (
Figure 1A).
There were 8 sets of transparent vinyl curtains with inside magnets installed in the aircraft to separate the clean and contaminated zones, with a semi-contaminated zone in the middle (
Figure 2). The medical staff and the flight crew took off their personal protective equipment (PPE) in the semi-contaminated zone and moved into the clean zone. The vinyl curtains were attached with double-sided adhesive tape, which created an air seal.
In the Boeing 777-200, there are 3 seats per row, and 2 seats in the back row (
Figure 1A). The asymptomatic passengers were seated in a zigzag formation to minimize the risk of droplet propagation through the air, from the patient sat behind. Symptomatic passengers were seated in the front of the aircraft, maintaining sufficient distance from the asymptomatic passengers, and enabling medical staff to access symptomatic passengers without passing asymptomatic passengers.
2. Pre-transfer quarantine
When the Iranian aircraft had parked alongside the Korean aircraft, 2 quarantine officers and a quarantine doctor wearing PPE entered the Iranian aircraft via a vehicle mounted scissor lift platform. The quarantine process was explained via the intercom on the aircraft, and the pre-filled Health Status Questionnaires (HSQs) and passengers’ body temperature were taken (
Figure 3A). Passengers who reported respiratory symptoms in the previous 14 days on the HSQ or who had a temperature of ≥ 37.5°C were immediately assessed for COVID-19 by the quarantine doctor (
Figure 3B). Passengers had a blue or a red sticker placed on their chest, depending on whether they were asymptomatic or under investigation, respectively, so that their COVID-19 status could be easily identified. One passenger with a mild sore throat and myalgia 2 weeks previously, who had a temperature of 37.9°C was categorized as a patient under investigation (PUI) by the quarantine doctor.
3. Passenger transfer, movement control, and education
Asymptomatic passengers disembarked from the Iranian aircraft first and moved to the Korean aircraft staying at least 2 meters apart from each other. A nurse stationed at the entry to the vehicle mounted scissor lift platform disinfected passengers’ hands, replaced their facemasks, and gave each passenger a package containing a hand sanitizer, an inflight behavior guide, a new HSQ, a pen, and an extra face mask (
Figure 3C). The crew assigned passengers’ seats prior to the passengers entering the aircraft to ensure optimal separation as passengers entered the front of the aircraft. The PUI boarded last and was assigned a prepared seat close to the entrance to the aircraft (
Figure 1B).
The quarantine doctor provided instructions on in-flight infection control practices before take-off. These included remaining seated (except when using the toilet), wearing a facemask (except during mealtimes), and frequently using the hand sanitizer provided. Passengers were instructed on how to use the toilet, using a disposable seat cover, closing the toilet to flush, reopening it, and pumping 3–4 squirts of dilute sodium hypochlorite into the toilet bowl (
Figure 3D). Passengers were instructed to wipe all the places that they touched with dilute sodium hypochlorite (dispensed onto a tissue). The PUI was given acetaminophen (paracetamol) 650 mg (× 4) to use if symptoms became severe.
4. Air-conditioning, designated toilets for symptomatic passengers, and in-flight services
Air flow into the engine is sterilized through the engine compressor, cooled, and flows into the cabin from above through a high-efficiency particulate air filter, so the air entering the cabin is relatively safe [
6]. A toilet located nearby the designated symptomatic passenger seats, was assigned to the PUI (
Figure 1A). For infection control, a meal, a snack, and sufficient water were provided in advance individually wrapped in a plastic bag to minimize the need for inflight service. The crew members who attended to the asymptomatic passengers wore N95 masks, gloves, and plastic vinyl aprons, and the crew members and medical staff who attended to the PUI wore Level D PPE. To ensure a safe long distance flight, the quarantine doctor taught the aircrew how to put-on and take-off the PPE, how to clean the cabin, and how to maintain personal hygiene before departing from Korea and Dubai.
5. Disembarking, airport quarantine, and medical waste disposal and cleaning
To exit the plane passengers left from back of the aircraft (
Figure 1C). The asymptomatic passengers exited first, and received a pre-quarantine screening at the arrival gate. The waiting quarantine officers checked the pre-filled HSQs, measured passengers’ body temperatures, and asked them about symptoms they experienced during the flight. Based on this screening, 1 additional passenger was categorized as a PUI on arrival.
The 2 PUIs were transported (using a prepared ambulance) to a negative-pressure isolation facility at Incheon International Airport Quarantine Station. The asymptomatic passengers had a respiratory swab collected for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing performed in a mobile laboratory outside the airport, and were transported individually to separate isolation quarters. The 2 PUIs had diagnostic samples collected in their isolated rooms at the quarantine facility. After all the passengers had disembarked from the aircraft, the quarantine doctor and a nurse wearing PPE, collected all the garbage left by the passengers, removed the vinyl curtains, and disposed them in a medical waste container. They also collected the medical waste including the protective clothing, gloves, and masks used in the semi-contaminated zone, and an infectious disease cleaning company was commissioned to disinfect the cabin.
Discussion
Several studies related to inflight infections have been published [
6–
8]. Most studies have dealt with the inflight mechanism of transmission, the effect of air conditioning on infectivity, and the effectiveness of wearing facemasks during a flight. This is the first practical account of prevention of infectious disease transmission in a high-risk group, during air evacuation, using full infection control and prevention measures.
The first PUI was determined not to be infected with SARS-CoV-2, but the second PUI tested positive for SARS-CoV-2. All those aboard the flight (passengers, aircrew, and medical staff) were screened for SARS-CoV-2 upon arrival in Korea and completed a mandatory 14-day medical quarantine. This account illustrates that transmission of infection can be controlled in long-distance flights if the aircraft cabin is thoroughly prepared in hospital infection control and prevention standards.
We hope that this account will serve as a guideline for infection control and prevention during future air evacuations during international infectious disease epidemics.
