Burden of Influenza-like Illness among military personnel receiving advanced training at Ft. Sam Houston, TX

Background: Influenza-like illness (ILI) places a significant burden on operational readiness in the U. S. military, particularly in trainees who live and work in congregated settings. ILI incidence rates for the trainees are based on passive surveillance of those presenting to medical clinics. Such clinic-based surveillance may under-estimate the true ILI burden because trainees with ILI may not seek health care due to mild symptoms or fear of missing training. We aimed to estimate the hidden ILI burden among trainees and behaviors related to healthcare seeking for ILI.

Methods: A 1-page voluntary, anonymous ILI survey was administered during the end of program sessions for military medical trainees at Fort Sam Houston (JBSA-FSH), TX. The survey was started in January 2017 and is ongoing.

Results: Between January and April 2017, 724 surveys were returned: respondents were aged 17-42 years (median 20 yo), 299 (41%) were female, and 442 (62%) white. The trainees maintained a healthy and active life style: 94% exercised at least 3 times a week; 79% never smoked and only 3% were obese. Overall, 68% trainees reported ILI symptoms during training: the proportion decreased from 75% in January to 46% in April (p-for-trend <0.01). History of travel and self-reported contact to people with ILI were associated with reporting having ILI. Of those reporting ILI, only 36% sought health care, and the proportion did not change over the four month period. Females were more likely to seek health care if they developed ILI: 43% of females vs. 31% of males (p=0.02). While the majority of trainees washed their hands or used hand sanitizer at least 4 times a day, only 60% of trainees washed their hands after covering their mouth/nose for a sneeze, which may facilitate ILI circulation in the population.

Conclusion: Among young and healthy medical trainees at JBSA-FSH, ILI was reported frequently during winter and decreased in spring. Trainees often did not seek health care for mild symptoms. The high prevalence of self-reported ILI among trainees despite their healthy life styles and good daily hand hygiene warrants further study. A better understanding of the impact of self-reported ILI on performance and of factors associated with health-care seeking are needed.