A COVID-19 Outbreak After a Spring Break Trip to Cabo San Lucas: University of Texas, 2020

On March 27, 2020, a University of Texas at Austin student with cough, sore throat and shortness of breath tested positive for SARS-CoV-2. Two more symptomatic students tested positive the next day, and the COVID-19 Center at University of Texas Health Austin (UTHA) opened an outbreak investigation. Contact tracing linked the cases to a spring break trip to Cabo San Lucas, Mexico, on March 14–19. The report was posted as an MMWR Early Release on June 24, 2020.

Contact tracing helped control a COVID-19 outbreak after a college spring break trip led to 64 cases. Figure from CDC's report.

The investigation

The UTHA COVID-19 Center, set up in early March with authority from Austin Public Health, ran testing, tracing and monitoring for the university.

• Finding people: tracers — medical and public health students and staff, supervised by a university epidemiologist and an infectious diseases physician — used interviews and flight manifests. Commercial-flight exposures went to the Texas Department of State Health Services.
• Groups: travelers; household contacts who lived with a traveler who tested positive; and community contacts with close contact elsewhere.
• Contact: a text, then up to three calls. Those without symptoms were told to quarantine and watch for symptoms for 14 days; those with symptoms were offered a test and told to isolate.
• Testing: nasal swabs at a drive-through site, run by RT-PCR. By March 30, 9 of the first 19 tested were positive, so testing widened to every traveler, with or without symptoms. Tests were scarce, so each person was tested once. The investigation ended on April 5.

Travelers had often shared hotel rooms in Mexico and apartments back in Austin, and some fell ill while still in Cabo San Lucas.

The 64 cases by exposure source and date of symptom onset, with the steps of the investigation, March 12–April 5, 2020. Figure from CDC's report.

Results

298 people were identified and 289 (97%) interviewed; 231 were tested — mostly non-Hispanic white students, median age 22, with few underlying conditions but nearly a quarter current smokers.

• 14 (22%) of those who tested positive had no symptoms when tested.
• The most common symptoms among positives were cough (21), sore throat (18), loss of smell or taste (15) and headache (14); only 6 had fever.
• Half of those who tested negative also had symptoms, and no set of symptoms distinguished COVID-19 — perhaps because other respiratory illness, including flu, was circulating.
• People with symptoms were more likely to test positive (odds ratio 3.5); smoking made no difference.
• No one was hospitalized, and no one died.

The response

Resources were pooled between the university and public health. University Health Services helped students with housing, food and other needs during isolation. Austin issued a shelter-in-place order on March 25; the university extended spring break a week and moved to remote learning from March 30; and both publicized the investigation and urged people to avoid nonessential travel and get tested if sick.

Lessons

• Silent infections are common in young, healthy people and likely sustain spread; test contacts whether or not they have symptoms.
• Shared housing — rooms in Mexico, apartments in Austin — meant repeated exposure, much as in long-term care facilities. Universities should align student housing with CDC guidance as they reopen.
• Coordination between schools and health departments speeds case finding, tracing and cluster detection.

Limits

• Most students were tested once, so some early or silent cases may have been missed.
• Seven people were tested elsewhere, and some forms were incomplete.
• The test's real-world sensitivity was unknown; similar tests had shown 2%–29% false negatives.
• Overlap between trip companions and housemates made primary and secondary infections hard to separate.

Sources

Based on Lewis M, Sanchez R, Auerbach S, et al., "COVID-19 Outbreak Among College Students After a Spring Break Trip to Mexico — Austin, Texas, March 26–April 5, 2020," MMWR Morbidity and Mortality Weekly Report, volume 69, Centers for Disease Control and Prevention; a work of the United States government in the public domain.