How A Trip To Mexico Triggered Coronavirus Outbreak Among 60 US students

On March 19, the day the Trump administration urged Americans to stop traveling internationally, a group of students from the University of Texas at Austin returned from a spring break trip to a Mexican beach resort.

Within two weeks, 60 of the 183 travelers to Cabo San Lucas, along with four contacts, tested positive for the novel coronavirus, according to a report from the Centers for Disease Control and Prevention.

As students prepare to return to many universities this fall, the case study offers a window into how easily covid-19 spreads among college students and, also, how it can be contained. Researchers likened their close quarters and constant interaction to the environment of a nursing home in the potential for disease spread.

"Contact tracing and testing of close contacts, regardless of symptoms, is important in limiting spread, especially in young and healthy populations living in shared housing," they wrote.

That effort limited the outbreak in this case, as did a local shelter-in-place order issued by Austin on March 25, six days after they returned, the researchers conclude.

At the time, reports of positive cases provoked outrage among local leaders.

Texas college students became ill after a trip to Cabo San Lucas.

"It's time to grow up," Texas House Speaker Dennis Bonnen, a Republican, said. "That is grossly irresponsible."

Parents of some students defended their decisions to allow the trip, saying they were told by the travel company JusCollege they could not get refunds if they canceled, because there was not yet a travel advisory to avoid Mexico.

The school began its investigation on March 28, after three of the travelers tested positive. They quickly identified the trip as a source of the outbreak through contact-tracing interviews. Although the first patient did not experience symptoms until the trip was over, some in the group became ill while in Mexico. The travelers were sharing hotel rooms during the trip and dorms or houses after their return to Austin. About half took a chartered plane together, according to the school.

"We take the safety of our customers very seriously and worked with public health authorities to assist with contact tracing where we could," said a spokeswoman for JusCollege. "It was an unprecedented and rapidly evolving situation, and our communications to our customers were being updated in line with the changing U.S. government guidelines."

Working with public health authorities, the school identified 298 travelers and close contacts and interviewed all but nine. Asymptomatic travelers and their contacts were advised to self-quarantine and monitor themselves for symptoms for 14 days. Symptomatic travelers and their contacts were offered tests and told to self-isolate until they got a negative test result, or for seven days after their symptoms began and three days without a fever. Ultimately, 231 people were tested.

But after half of the first batch of tests came back positive, the school decided to test anyone who had traveled to Cabo. Beyond April 2, two weeks after the travelers returned, tested continued only for symptomatic travelers and contacts. The investigation ended April 5, when the last symptomatic contacts got negative test results.

The median age in the group was 22. Although 78 percent of those who tested positive experienced symptoms, none required hospitalization and none died. The most common symptoms were cough, sore throat, headache and loss of sense of smell or taste.

"Asymptomatic persons or those with mild symptoms likely play an important role in sustaining SARS-CoV-2transmission during outbreaks, especially in younger populations, such as the one described here," the researchers wrote.

Half of those who tested negative also experienced symptoms. The researchers suggest that those patients may have lied about symptoms to get a test early in the investigation, or contracted a flu variety going around at the time. They also note that coronavirus tests have a false negative rate of up to 29 percent. Most students were only tested once, so some cases might have been missed.