How four passengers got the coronavirus in …

An epidemic aboard a 18 hour flight from United Arab Emirates to New Zealand It offered researchers in this Oceania country the opportunity to study infections in transit. As they were able to reconstruct, on September 28, the Emirates Airlines Flight 448 started from Dubai to Auckland with 86 passengers on board and a full crew: as of October 8, seven of these people had tested positive. Using siege maps and genetic analysis, the new study determined that some of the infections would have occurred during the flight, after a passenger started a chain of infection that spread to others on the road.

The study was conducted by the New Zealand Ministry of Health and the New Zealand ESR Laboratory Agency. It has not yet been reviewed by other scientists but brings it to light potential for transmission of the coronavirus during air flights. Although the airline industry has conducted research indicating the risk is low, this is the second case of in-flight transmission in New Zealand.

The seven passengers tested positive of covid-19 after arriving in Auckland they came from five countries and they were seated with the layout shown in the following graphic:

Of of them (cases C and E) recognized that they weren’t wearing masks. Rest, Of (A and B) recognized that removed their sleeping masks and sat down, which implies that they only used them while walking on board.

The airline did not require the use of a mask in the lounge before boarding. It also does not need pre-flight testing, although in the days prior to boarding, five of the seven passengers who subsequently tested positive had been tested and received negative results.

Cases

Sitting in seats 26D and 26G, a Swiss couple is suspected to be at the origin of the small transmission chain. The couple, the study explains, took the coronavirus test on September 24, three days before leaving Zurich for Dubai. These results were negative. But after arriving in New Zealand, one of the two began to develop symptoms.

Tagged as Case A, this person began to experience muscle pain and general weakness on October 1, two days after arriving at the compulsory isolation center in New Zealand. Her partner developed symptoms, the same as in Case A, more cough and runny nose the next day (both tests on day 3 were positive). “The Ministry of Health considers people to be contagious two days before symptoms appear, so case A is treated as the only contagious person on the plane, although the Case B he may have been infected at that time, ”explains the New Zealand newsroom. Case B, researchers said, was likely infected from the same source as case A or case A.

The other Day 3 tests for flight EK448 were also negative, except for one, labeled as Case C: He was asymptomatic throughout his illness, according to the study, and sat in seat 24C (across the aisle and two rows in from Case A). He traveled from Kiev in Ukraine to Dubai before boarding the plane for Auckland.

he case E, who also did not develop symptoms of his illness, tested positive on October 6. He was sitting two rows behind Case B and had come to Dubai from Kochi, India. he case D, who sat directly behind Case A and flew to Dubai from Dublin, developed congestion, headaches, colds, muscle aches and other symptoms between October 4-7, date he tested positive.

he case F developed congestion and cough on October 2, but tested negative on day 3 that day. He had come to Dubai from Johannesburg with three other family members, including the possible Case G. When all four were tested again on October 8, cases F and G tested positive while both of their parents tested negative. When the results arrived, case G was asymptomatic, but the next day he developed congestion and a sore throat. The family had sat in two rows opposite Cases A and B, but had swapped seats throughout the flight.

Investigators believe Case G was not infected during the flight, but was infected with Case F while sharing a room in controlled isolation.

What the genomes say

When New Zealand researchers got the results of genome sequencing of EK448 cases – a common procedure for tracking potentially dangerous mutations – they noticed something strange. “We found that many genomes in this scan, which was a routine surveillance scan, were relatedJemma Geoghegan, evolutionary virologist at the University of Otago and a key member of the country’s covid-19 sequencing team, told the newsroom.

“We investigated further because they were not part of a family group and some of them were in different quarantine facilities. Then, speaking to the contact followers, it turned out that they were all on the same flight. So, through further investigation, it was found that in fact, They were from quite geographically separated countries, but they only took the same flight from Dubai, so their connecting flight was the only time they were actually in contact.“said the researcher.

Cases A, B and C then they became natural suspects of the source of the infection, Geoghegan said. It is because they gave positive on day 3 and therefore the previous days would have been more likely to be infectious. “Between cases A and B, the case A symptom developed the day before and that would have meant it was contagious by the middle of the 6pm flight. During this time, Case C never developed any symptoms, which makes it much more difficult to estimate a probable infectious period, ”says Newsroom in the note reporting on the study.

Solving this mystery became much easier when the seven genomes were compared to the International Register. The variant of the virus that infected these seven people had five mutations that set it apart from the “original” sequence of SARS-CoV-2 recorded in early January. There are only six virus genomes in the GISAID database, which contains over 212,000 sequences, which match that found in the EK448 cases. All were checked in between September 2 and 23 (a few days before the flight from Dubai) and all were in Europe.

Two of the sequences are from the UK, which has sequenced almost half of the genomes available from GISAID. The other four met in Switzerland. This strongly led investigators to conclude that cases A and B led to Covid-19 to flight EK448.

Investigators also acknowledged that transmission was possible at Dubai Airport. However, they noted that the fact that the seven cases were within four rows of each other, and within two rows of the probable index cases, was a clear indication that transmission had taken place on board.

“These findings are supported by genome sequencing, an onboard seating plan and the dates of disease onset. This data does not definitively rule out an alternative exposure event such as transmission that occurs at Dubai Airport prior to boarding. for example, during check-in or boarding queues. However, the proximity of the affected passengers on board during the flight suggests that the in-flight transmission is plausible, ”the researchers argued.

Importance of maintaining isolation and protective measures

“This shows the importance of managing isolation and quarantine. The idea that people can test negative and then get on a plane and everything is fine is clearly ludicrous.. People can hatch, they can get infected a few days before they fly. Again, this is good evidence that pre-flight testing, even if it would prevent infected people from getting on the plane, won’t catch everyone, ”one of the researchers said.

For academics, “the fact that three passengers tested positive on the third day of their 14-day quarantine period indicates that some of the complexity of determining the value of pre-departure tests, including the modality and timing of said tests “.