The biggest challenge with how easily SARS-CoV-2 spreads is that pre-symptomatic people are perhaps the most likely to infect others. Some studies suggest that people shed the most virus in the two days leading up to symptoms. So taking temperatures, convincing people to stay home when sick, only goes so far. That’s why healthy people are asked to wear masks, because they may be infecting others without realizing it.
Another big problem though is that even people who test positive for the virus aren’t staying home. Some are hiding their diagnosis, and still traveling. When United began requiring passengers to complete a health screening prior to travel it seemed odd to me – anyone pre-symptomatic wouldn’t know they have the virus, anyone sick would either stay home or lie.
Since Hong Kong tests passengers on arrival, and aggressively tracks contacts and interviews patients, they know about cases where people who tested positive flew anyway.
Hong Kong’s health authority said one infected passenger arrived Sunday from Manila on a Cathay Pacific Airways Ltd. flight, and another was on a Cathay Dragon flight from Kuala Lumpur. Both were diagnosed with Covid-19 before they traveled.
…Biogen Inc. said in March it fired a female worker who returned to China from Massachusetts without disclosing her infection. Local media said the 37-year-old took a large dose of anti-fever medication before she boarded to hide her illness.
…JetBlue Airways Corp. banned a passenger who flew from New York to Florida and notified the crew after landing that he had tested positive for coronavirus
Taking temperatures may help identify people with one common symptom of COVID-19, but people with a low grade fever can take over the counter pain killers like Tylenol (acetaminophen), ibuprofen, aspirin, or naproxen.
Right now in Austin it appears to be taking 4-8 days to receive test results. People getting the free public test report being told it could take as long as 10 days for results. People are recovering from the virus before they confirm they had it.
Suspected positives aren’t required to quarantine. Indeed even those who test positive aren’t being forced to quarantine. And what does contact tracing even look like, at least in my home town?
[E]very day, more than a thousand test results are faxed to Austin Public Health, rather than reported digitally. APH staff members must then sift through the results manually. And in some cases in which people have tested positive, Escott says, the faxed test results don’t include contact information for patients, so staff members have to do detective work to track them down before they can make contact tracing calls.
So between people who don’t know they have the virus, and people who do and choose not to stay home, there’s continued spread – including people flying. The good news is that masks do appear to help limit spread but most importantly flights themselves haven’t been found as a vector for significant spread. There haven’t been case clusters tied back to being on the same plane. Instead it appears people flying with the virus brings the virus from one place to another.
That’s not significant risk where the virus is already spreading, as it is right now in parts of Texas, Florida, Arizona and California – but it’s a bigger deal where the virus is currently under control.
When I drafted this I initially wrote that “it won’t surprise me, then, to see other states follow the lead of places like Hawaii (and previously Texas) imposing quarantines on flight arrivals from certain states.” And that’s already what’s happened with New York, New Jersey, and Connecticut “ordering a mandatory 14-day quarantine on visitors from states with high numbers of COVID-19 cases.”
- The list of states is to include those “with an infection rate of 10 per 100,000 on a 7-day rolling average or 10 percent of the total population positive on a 7-day rolling average.” (By the way this is a lower threshold than Europe is considering.)
- Currently that means Alabama, Arkansas, Arizona, Florida, North Carolina, South Carolina, Washington, Utah, and Texas.
So far these sorts of quarantines have been implemented based on arriving flights, which is only a limited proxy for where someone is traveling from. Connect through a third non-outbreak state and avoid the quarantine, while anyone connecting in say Dallas or Phoenix might be subject to quarantine even though they never did more than go beyond the airport.
Governor Cuomo suggests this will apply to drivers and that “police will be stopping cars with out of state plates in New York” and that “hotel employees should be questioning guests about their quarantine.”