key: cord-0918875-ikepa1lm
authors: A, Pavli; P, Smeti; S, Hadjianastasiou; K, Theodoridou; A, Spilioti; K, Papadima; A, Andreopoulou; K, Gkolfinopoulou; S, Sapounas; N, Spanakis; A, Tsakris; HC, Maltezou
title: In-flight transmission of COVID-19 on flights to Greece: an epidemiological analysis
date: 2020-09-17
journal: Travel Med Infect Dis
DOI: 10.1016/j.tmaid.2020.101882
sha: eaa3c203df11df6e2d2226d0050149206991c3ae
doc_id: 918875
cord_uid: ikepa1lm

BACKGROUND: The emergence in China in late 2019 and subsequent progression of a pandemic of a respiratory disease named coronavirus disease 2019 (COVID-19) was highly facilitated by international travel. We present 5 cases of probable in-flight transmission in Greece. METHODS: We studied international passengers arriving to or departing from Greece from February 26 through March 9, 2020. Contact tracing extended up to 4 days before the onset of symptoms and focused on close contacts. Close contacts were defined as persons sitting within a distance of < 2 meters for > 15 minutes, including passengers seated two seats around the index case and all crew members and persons who had close contact with the index case. RESULTS: We investigated 18 international flights with 2224 passengers and 110 crew members. Main countries of departure included Northern Italy, Israel and the United Kingdom. In accordance with the national surveillance investigation, in these flights there were 21 index cases and 891 contact traced cases. Six index cases were symptomatic during the flight. Of the 891 contact traced cases, 4 passengers and 1 crew member developed laboratory-confirmed infection (3 with COVID-19 and 2 with asymptomatic infection); they travelled on the same flight with two COVID-19 cases. CONCLUSIONS: Air travel has played a central role in the progression of the COVID-19 pandemic. However, there are scarce data about in-flight transmission. Our extensive investigation showed five cases of probable in-flight transmission. Efforts should be placed in order to ensure the prompt implementation of appropriate infection control measures on board.

The emergence in China in late 2019 and subsequent progression of a pandemic of a respiratory disease named coronavirus disease 2019 (COVID-19) was highly facilitated by international travel. We present 5 cases of probable in-flight transmission in Greece.

We studied international passengers arriving to or departing from Greece from February 26 through March 9, 2020. Contact tracing extended up to 4 days before the onset of symptoms and focused on close contacts. Close contacts were defined as persons sitting within a distance of < 2 meters for > 15 minutes, including passengers seated two seats around the index case and all crew members and persons who had close contact with the index case.

We investigated 18 international flights with 2224 passengers and 110 crew members. Main countries of departure included Northern Italy, Israel and the United Kingdom. In accordance with the national surveillance investigation, in these flights there were 21 index cases and 891 contact traced cases. Six index cases were symptomatic during the flight. Of the 891 contact traced cases, 4 passengers and 1 crew member developed laboratory-confirmed infection (3 with COVID-19 and 2 with asymptomatic infection); they travelled on the same flight with two COVID-19 cases.

Air travel has played a central role in the progression of the COVID-19 pandemic. [2, 3] . Factors that increase the risk of in-flight transmission of respiratory pathogens include the possibility of airborne spread, transmissibility during asymptomatic, mild or pre-symptomatic periods as well as long incubation period [3] .

In Greece the first COVID-19 case was diagnosed in Thessaloniki on February 26 in a traveller returning from Italy and was followed by another 4 imported cases in Athens [4, 5] . The aim of this report is to describe five cases with SARS-CoV-2 infection of probable in-flight transmission during a commercial flight carrying the first imported cases in Greece.

We recorded information on contact tracing performed from February 26 through March 9, 2020 on international flights to and from Greece. Criteria for in-flight contact tracing included travel of an index case within 1-4 days prior to symptom onset or while being symptomatic, based on a mean incubation period of five days (range: 2-14 days) of COVID-19 [6] . Contact tracing focused on close contacts (distance of < 2 meters for > 15 minutes), including passengers seated two seats in all directions around the index case and all crew members and persons who had close contact with the index case (e.g. travel companions or persons providing care) [6, 7] . Advice was provided to all close contacts for 14-day self-quarantine following their last exposure and self-monitoring for respiratory symptoms and/or fever and to 

to and from Greece during the study period (Table 1) [10, 11, 12] . Our extensive investigation revealed five SARS-CoV-2 infected cases of probable in-flight transmission and particularly in four passengers and one crew member on a flight from Israel to Athens. Acquisition of infection in Greece shortly after arrival is highly unlikely, given that no local transmission was documented in Athens during that period of time. In particular, the first imported cases in Greece were diagnosed on February 26 [5] . Similarly, in Israel there was only one case reported at that time. Further information collected by telephone showed that crew members on flight from Israel to Athens did not leave the airport gate after arriving from Athens to Tel Aviv and that they embarked shortly after arrival on a return flight. Therefore, exposure to local circulation of SARS CoV-2 in Israel, a country with only one case reported during that period, is extremely unlikely.

However, exposure of the two pilgrim index cases in Jerusalem and subsequent inflight spread of the disease can be justified considering that pilgrims constitute a high-risk group of travellers for acquisition of respiratory diseases [13] 

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We thank the participating airlines for their assistance.

All authors declare no competing interests.

No ethical approval was required.J o u r n a l P r e -p r o o f