Influenza B, Q fever, and the consequences of febrile illness occurring during jungle warfare training: a clinical and serological study.

Seventy-one Royal Marines undergoing jungle warfare training were studied clinically and serologically to determine the incidence and consequences of febrile illness. During acclimatization and the early part of the deployment the incidence of illness having an impact on training was low; during the latter part an outbreak of influenza B occurred, with 25 cases diagnosed clinically. Only 12 of these were confirmed serologically, probably because the outbreak was still in progress when the second samples were taken. A further four subclinical cases were uncovered by the serological study. Five cases of heat exhaustion occurred, one Marine suffering two episodes. Four patients required case-vac from the jungle. Three Marines were found to have serological evidence of previous acute Q fever, including the patient who had two episodes of heat exhaustion. This incidence is higher than expected, and warrants further investigation.