Risk of asymptomatic transmission on planes

Risk of asymptomatic transmission on planes - Printable Version

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Risk of asymptomatic transmission on planes - BostonCard - 08-28-2020

https://wwwnc.cdc.gov/eid/article/26/11/20-3353-f1

Looks like there were 6 asymptomatic COVID-19 carriers on a flight from Milan to South Korea, and 293 asymptomatic passengers who were negative for COVID-19. Of those 293, only one contracted COVID-19 (so about 0.3% risk), and that was a *long* flight.

[Image: 20-3353-F1.jpg]

By the way, it does show the pitfalls of mask wearing: "On the flight from Milan, Italy, to South Korea, she wore an N95 mask, except when she used a toilet. The toilet was shared by passengers sitting nearby, including an asymptomatic patient. She was seated 3 rows away from the asymptomatic patient (Figure)." Obviously there is no way to know whether the patient inhaled droplets in the bathroom when she took her mask off or if it was transmitted via surfaces.

Note that they also looked at a second flight:

Quote:Another evacuation flight of 205 passengers from Milan, Italy, to South Korea on April 3, 2020, was also conducted by KCDC under strict infection control procedures. Among the passengers on this flight were 3 asymptomatic patients who tested positive on quarantine day 1 and 1 patient who tested negative on quarantine day 1 and positive on quarantine day 14. On the basis of an epidemiologic investigation, the authors and KCDC suspect that this infection was also transmitted by inflight contact.

I would feel better about flying after seeing this data, which is much more reassuring than similar analyses during the SARS pandemic.

BC

RE: Risk of asymptomatic transmission on planes - oldalum - 08-28-2020

and she took her mask off in the lavatory because . . . ????!!! A small confined space with I think no ventilation.

My impression from reports of the study is that the authors conclude the infection was most likely from aerosols, not surfaces. They probably inquired about hand washing in the lavatory. And if the infection had been transmitted via a surface, maybe another passenger would have turned positive as well. But unclear--did the infected transmitter create aerosols despite wearing a mask? Or did that person take his or her mask off in the lavatory too?

Still, effectiveness of masks again demonstrated, despite middle seats being occupied.

RE: Risk of asymptomatic transmission on planes - g1313 - 08-28-2020

Thanks BC. Personally I would love to get on a plane, but the big question for me would be how many of the characteristics of this special evacuation flight (for Koreans, presumably) exist on a typical commercial flight. A few factors that would be highly concerning to me:

The study says most people on this flight were wearing N95s. They might have also been given training on proper usage of a N95.
6 out of 299 passengers were positive, or 2%. Is that much lower than we would expect on a typical flight? Some estimates of prevalence in outbreak states like NY were as high as 8%?

Still, relatively good news that people who are choosing to fly have pretty good odds, although not sure how to think about the risks of a superspreading event on a plane.

lex24 - lex24 - 08-28-2020

I flew in early August. Delta. 4 hours. 60%-70% capacity. No middle seats. Masks mandatory. No food (just a bag with water and a snack). Boarding is done by back rows moving forward.

I stayed away from people as much as possible in airport. SFO was a ghost town. Other airport more busy. But still very easy to massively distance. Security was a little nerves inducing. But they distance a bit, and there was sanitizer available as soon as I got through.

Got home on a Monday and self quarantined for a week.

I understand I was taking a bit of a risk. But I thought it was an acceptable one.

RE: Risk of asymptomatic transmission on planes - BostonCard - 08-28-2020

(08-28-2020, 04:52 PM)oldalum Wrote: and she took her mask off in the lavatory because . . . ????!!! A small confined space with I think no ventilation.

My impression from reports of the study is that the authors conclude the infection was most likely from aerosols, not surfaces. They probably inquired about hand washing in the lavatory. And if the infection had been transmitted via a surface, maybe another passenger would have turned positive as well. But unclear--did the infected transmitter create aerosols despite wearing a mask? Or did that person take his or her mask off in the lavatory too?

Still, effectiveness of masks again demonstrated, despite middle seats being occupied.

Some people shed SARS-CoV-2 in their stool, which may get aerosolized when the toilet is flushed. All the more reason to wear an N95 in an public restroom, pandemic or not.

That being said, I agree with you; the study shows that masks (and especially N95 masks) by and large work. Note that although they say "most passengers wore masks", they didn't specifically say if the asymptomatic carriers did.

BC

RE: Risk of asymptomatic transmission on planes - fullmetal - 08-28-2020

I'd feel better about flying if everyone wore a mask, but given the high-profile incidents of people trying to die on a hill making a statement lately...I'd like to not get caught with one aboard my flight. Also, as people get more comfortable with flying, those airports are just going to get more crowded...

RE: Risk of asymptomatic transmission on planes - murky - 08-31-2020

(08-28-2020, 04:52 PM)oldalum Wrote: and she took her mask off in the lavatory because . . . ????!!! A small confined space with I think no ventilation...

Perhaps to wash her face, blow her nose, or sneeze?