(CNN)A spring break trip to a Mexican beach resort last March led to 64 cases of coronavirus, but proper contact tracing, quarantine and isolation got the outbreak under control.
No one got seriously ill and no one died, but the incident illustrates how young people -- especially college students -- can quickly spread the virus among themselves and carry it into the community, a team at The University of Texas at Austin reported Wednesday.
The students had traveled to Cabo San Lucas, Mexico, from March 14-19. A week later, back in Austin, three showed up at the University of Texas Health Austin (UTHA) health center with coronavirus symptoms and tested positive.
Ultimately, 60 vacationers caught the virus. They in turn infected one household contact and three people in the community, the UT team reported in the US Centers for Disease Control and Prevention's weekly bulletin.
"Contact tracing interviews revealed that Cabo San Lucas travelers used a variety of commercial, charter, and private flights to return to the United States," wrote the researchers, part of a joint effort between the university and Austin Public Health.
"Additional travelers were identified through contact tracing interviews and review of flight manifests gathered with assistance from Austin Public Health," they added.
Then the contact tracing team swung into action. "UTHA trained medical students, public health students, and clinical and research staff members to trace contacts. UTHA contact tracers communicated with travelers and contacts by telephone, first texting an initial message about the potential exposure and then attempting to call each traveler and contact up to three times," they wrote.
"During the telephone call, contact tracers advised asymptomatic travelers and contacts to self-quarantine and self-monitor for symptoms for 14 days from the last potential exposure date. Symptomatic travelers and contacts were offered a SARS-CoV-2 test and asked to self-isolate until either a negative test result was obtained or, following CDC recommendations at the time, until 7 days after symptom onset, including 3 days with no fever and no worsening of symptoms."
It was complicated, because many of the people involved had shared rooms, traveled together, and then returned home to shared apartments. And about a fifth of those who ended up testing positive had no symptoms.
"Asymptomatic persons or those with mild symptoms likely play an important role in sustaining SARS-CoV-2 transmission during outbreaks, especially in younger populations, such as the one described here," the research team wrote.
The symptoms people did have were various. "Similar proportions of fever, cough, sore throat, and headache occurred among persons with positive test results and those with negative results," the team wrote.
It's possible some of the students had other respiratory infections, including the flu. The researchers also suspect some claimed they had symptoms when they did not, so they could get tested.
As for the implications from the study, the researchers said universities, colleges and other schools need to take into account this pattern of shared living and rapid virus spread as they consider reopening.
Cases surge in Texas
"Because the spread is so rampant right now, there's never a reason for you to have to leave your home," Gov. Greg Abbott told CNN affiliate KBTX. "Unless you do need to go out, the safest place for you is at your home."
New cases and hospitalizations there are rising at their fastest rate yet -- something Abbott called "unacceptable" -- with Texas reporting more than 5,000 cases in a single day, breaking its previous record, health authorities said.
Additional reporting from CNN's Jay Croft and Christina Maxouris