Arboviruses in UK Armed Forces: a review of historical cases and identification of future threats.

Introduction: Arboviruses are a diverse group of arthropod-borne pathogens and are emerging global public health threats with no approved therapeutics. Arboviruses are spreading rapidly, posing a health threat to UK Armed Forces (UKAF) service personnel (SP) through deployment to endemic regions. There are limited data on the burden of arboviral infections in UKAF SP.

Methods: A retrospective service evaluation of UKAF electronic healthcare records (eHRs) and statutory notifications to the Defence Public Health Unit was conducted. Cases with possible/confirmed dengue, chikungunya or Zika virus infections between 2005 and 2023 were included. eHRs were interrogated and trends analysed.

Results: Of 107 suspected infections between 2005 and 2023, 49 (45.8%) were laboratory-confirmed. Dengue fever was the most common (45/49) followed by chikungunya (3/49) and Zika (1/49) virus infections. The average yearly incidence of reported dengue infection increased from 0.51 cases per 100 000 UKAF SP per year in 2009-2011 to 3.85 cases per 100 000 SP per year in 2021-2023. 19/45 (42.2%) cases occurred during operational deployments and 24/45 (53.3%) during non-military activity. Dengue infection was most frequently acquired in Southeast Asia.Using WHO clinical severity criteria, 33/45 (73.3%) had dengue with warning signs and 5 (11.1%) had severe dengue. 23/45 (51.1%) dengue cases were hospitalised (median length of stay 5 days, IQR 3, range 1-9). No dengue fatalities or medical discharges occurred. Occupational impact was significant, with a median of 11 days stood down (IQR 10, range 0-45); 3/19 (15.8%) cases on operations required aeromedical evacuation (AEROMED). One deployed case of chikungunya required AEROMED and a 35-day downgrade.

Conclusions: Reports of arboviral infections, particularly dengue, are increasing in UKAF personnel, presenting an emerging health threat. This has implications for UKAF provision of deployed diagnostics and dengue vaccination policy. The rapid spread of arboviruses outside their traditional geographical areas, including into Europe, necessitates further surveillance and requires diagnostic and therapeutic research.