Volume 18, Number 5—May 2012 Unsuspected Rickettsioses among
Patients with Acute Febrile Illness, Sri Lanka, 2007 We studied
rickettsioses in southern Sri Lanka. Of 883 febrile patients
with paired serum samples, 156 (17.7%) had acute rickettsioses;
rickettsioses were unsuspected at presentation. Additionally,
342 (38.7%) had exposure to spotted fever and/or typhus group
rickettsioses and 121 (13.7%) scrub typhus. Increased awareness
of rickettsioses and better tests are needed. Globally,
rickettsioses are increasingly recognized as causes of
undifferentiated fever. Paired serum samples are infrequently
obtained, but testing acute-phase serum alone is insensitive
(IgG is initially absent) and nonspecific (IgG can persist for
years, and IgM results represent cross-reactions). Sentinel
studies in Malaysia (1), Thailand (2), India (3), Laos (4), and
Nepal (5) suggest that scrub and murine typhus are frequent and
that misdiagnosis as enteric fever results in ineffective
therapy (5). Unrecognized rickettsial speci