Simulations of college campus mpox outbreaks show importance of detection, isolation

Future outbreaks of mpox on college campuses could be contained with timely detection and isolation of symptomatic cases, a study found.

While CDC data show that mpox cases have declined in the United States since the outbreak’s peak in July and August 2022, Alexandra Savinkina, MSPH, a PhD student at Yale School of Medicine, and colleagues noted that men who have sex with men (MSM) are still a vulnerable population, as are individuals in educational settings since persons of college age represent half of all sexually transmitted infections in the country.

“Thus, mpox may still emerge, if even sporadically, among young MSM and other sexually active persons, including on college campuses, with ongoing public health and economic implications for these institutions,” they wrote in Annals of Internal Medicine.

The researchers used a mathematical model to estimate the likelihood of an mpox outbreak occurring in a residential college setting and to determine how it might spread. They also analyzed the impact of interventions such as case detection, isolation, quarantine and vaccination.

The stochastic dynamic model, titled SEIR, simulated transitions between four stages: susceptible, pre-symptomatic, symptomatic and recovered.

The study cohort consisted of 6,500 hypothetical college students, who were divided into low- and high-risk infection groups. At the beginning of the semester, if just one person was infected and thus categorized as high risk, all other students were classified as susceptible.

The high-risk group consisted of 650 students, or 10% of the total cohort, based on estimates of the MSM population aged 18 to 24 years.

Following 1,000 simulations of mpox transmissions, Savinkina and colleagues found that, without detection and isolation of students, there was an:

• 82% chance of an outbreak within the high-risk group; and
• 83% chance of cases in the low-risk group.

This resulted in a mean additional 124 cases (95% CI, 3-326) for the high-risk group, and 59 cases (95% CI, 1-184) for the low-risk group.

With detection and isolation of symptomatic individuals, the chances of an outbreak in the high-risk group decreased to 51%, and the likelihood of cases in the low-risk group decreased to 29% when 80% of cases were detected.

The researchers noted that the mean number of cases dropped to below 10 when 80% of cases were detected for both groups.

“The maximum isolation capacity needed was 47 when 50% of students were detected and isolated,” they wrote.

Reactive vaccinations did not reduce the likelihood of an outbreak when 50% of cases were detected and isolated, nor did quarantines, according to Savikina and colleagues. However, both reduced the average number of cases when the high-risk group had a basic reproductive number of 2.4.

Additionally, “when assuming 50% of those in the high-risk group were preemptively vaccinated for mpox before the start of simulation, the likelihood of an outbreak beyond the initial cases was reduced,” the researchers wrote. “Assuming no detection and isolation, the likelihood of outbreak was 76% in the high-risk group and 78% in the low-risk group.”

When detection and isolation were assumed to be below 80%, the mean number of cases declined by 33% to 82% for the high-risk group and 50% to 72% for the low-risk group.

Savinkina and colleagues said the model “provides the basis of a contingency plan for college administrators” in the event of mpox spread on a residential campus.

“Our study clearly shows that without any intervention to address the introduction of

mpox on a campus, an outbreak is likely to ensue; thus, preparing for such an eventuality is a prudent course,” they wrote, pointing out that because the demonstrated interventions are simple and effective, planning for outbreaks “offers few downsides for administrators.”

References:

• Savinkina A, et al. Ann Intern Med. 2023;doi:10.7326/M22-2734
• U.S. mpox case trends reported to CDC. https://www.cdc.gov/poxvirus/monkeypox/response/2022/mpx-trends.html. Accessed Jan. 27, 2023.