On Dec. 29, 2020, the United States discovered its first known case of a highly contagious coronavirus variant, first identified in the United Kingdom, in a Colorado man with no travel history. The man’s lack of prior travel meant the more deadly version of covid-19 was already spreading in the United States, leaving Americans wondering how it got here.
“It didn’t teleport across the Atlantic,” William Hanage, a Harvard University epidemiologist, told the New York Times at the time.
And as news reports of the initial case of the variant (known as B.1.1.7) broke that week, a separate case of that variant boarded a flight from London to Dallas. We now know this because of Centers for Disease Control and Prevention reports released Wednesday about the first detected travel-linked cases of two coronavirus variants.
The agency detailed in one case study how a 61-year-old passenger infected with the B.1.1.7 variant boarded a Dallas-bound flight Dec. 31 despite being symptomatic for covid-19. In another case study, the agency outlined how a traveler from Brazil became the first known U.S. case of the variant identified in Brazil (P.1).
While the first documented case of B.1.1.7 in the United States was one of community spread, the first known P.1 case in the U.S. was identified in a traveler.
The CDC detailed that travel case in a report released Wednesday which said the P.1 variant, which experts suspect can reinfect individuals who already had covid-19, arrived on an early January flight to Minnesota from southwestern Brazil. The infected traveler was hospitalized in Minnesota 14 days after exposure to the virus, and no secondary cases were confirmed by the CDC, despite dozens of close contacts of the traveler being tested for the variant, including hospital staff, according to the report. The agency said it did not contact trace the flight’s passengers because 19 days had passed since the patient’s flight.
In the case of the variant found in the U.K., the passenger flying from London to Dallas on Dec. 31 had tested negative for the coronavirus as required via a rapid antigen test three days before traveling, the report said. But the traveler developed nasal congestion the day before travel and more severe symptoms after landing in the United States. The traveler was permitted to fly the 10 hours to Texas despite disclosing congestion on a preflight health survey and subsequently tested positive for the coronavirus in the United States on Jan. 2. Upon arrival on New Year’s Eve, the traveler stayed in a hotel overnight before an eight-hour drive to Corpus Christi, Tex., that saw five road stops for food and gas.
The agency did not detail any confirmed cases linked to that traveler, and it did not contact trace the flight’s passengers, this time because 12 days had passed since travel. It remains unclear which airline either passenger traveled with.
“As part of the contact investigation, Texas DSHS shared the patient’s flight information with the CDC El Paso Quarantine Station on January 11,” the CDC report said. “Because 12 days had passed since the flight, CDC did not initiate an aircraft contact investigation; however, CDC later provided an informational notification to the states because of the variant case.”
The case studies demonstrate how travel can facilitate the spread of covid-19 variants across the globe, the CDC said, and shows the need for restrictions like testing both before and after travel, as well as self-quarantine and physical distancing.
It also shows that the new U.S. requirements for all entrants to present a negative coronavirus test taken within three days of departure can falter, such as in the U.K. traveler’s case, by allowing rapid tests, which can miss early cases of covid-19. The report notes that the passenger’s initial rapid test, which was required for U.K. travel to the U.S. at the time, had “the potential for false-negative results” because of the timing of the test.
The CDC also stated that “predeparture testing should be considered one component of a comprehensive travel risk management strategy” that includes testing both before and after travel along with mask-wearing, distancing, hand-washing, self-monitoring for symptoms, and a period of self-quarantine after travel.
The CDC has not responded to request for clarification on what its typical practice is for contact tracing airplane exposure to a confirmed coronavirus variant case. On its website, the agency says it is responsible for contact investigations involving flights to the U.S. or between states, and that timing of the reported cases can vary greatly.
“Sometimes CDC is notified about a sick traveler while the plane is still in the air or shortly after the plane has landed,” the CDC website states. “However, in most cases CDC is notified when a sick traveler seeks treatment at a medical facility. These notifications can be made days, weeks, or even months after the travel.”
More than 2,500 confirmed cases of the B.1.1.7 variant and 13 cases of the P.1 variant have now been found in the United States through randomly performed genome sequencing of samples, which the CDC says does not represent the total number of variant cases in the United States — the actual total is probably higher. The variant identified in South Africa (B.1.351), which is also more contagious, was discovered in South Carolina in late January in two unrelated people with no travel history, and the U.S. has confirmed at least 65 cases of that variant since then, according to the CDC.
The state with the most reported cases of coronavirus variants is Florida, which has confirmed more than 500, according to the CDC. Second is Michigan, with more than 400 confirmed variant cases, and third is California, with more than 200. The primary variant found in all three states was B.1.1.7.
“CDC recommends that people avoid travel at this time,” the CDC says on its website. “However, for those who must travel, additional measures have been put in place to increase safety; especially as COVID-19 variants spread around the world.”
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