Measles Without Rash During Acute Febrile Illness Surveillance in Tanzania, 2023-2024

The leading causes of fever requiring hospital admission in rural sub-Saharan Africa remain understudied, particularly using modern molecular diagnostics.

We enrolled 258 patients with acute fever (cases) and 48 controls admitted to 1 hospital in Tanzania for 1 year starting in February 2023. Blood was tested by blood culture, polymerase chain reaction (PCR) for 35 pathogens, and serology for 6 pathogens.

The leading pathogen detected in cases was measles, with 70 of 258 cases detected by PCR, 74 of 238 by immunoglobulin M serology, and 91 allowing either method. Other pathogens were detected in <5% of cases including, in descending order, Plasmodium, Schistosoma, and Bartonella, among others. Measles was the only pathogen clearly associated with cases versus controls. Of 91 measles cases, only 58 (64%) were clinically suspected and only 56 (62%) met the World Health Organization definition of a clinical measles case, largely because 27 (30%) measles cases did not have recorded rash. Outcomes were poorer for measles without rash versus with rash, with a longer hospital stay (mean, 5.5 vs 3.3 days; P = .010), less full recovery (48% vs 75%; P = .016), and high mortality (7% vs 2%; P = .20). Increased laboratory testing would have detected measles 2 months prior to the first clinical suspicion.

Measles was found to be the leading cause of fever during 1 year of acute febrile illness surveillance in rural Tanzania. Measles can present without notable rash in these settings and has poor outcomes. Increasing laboratory test availability and clinician suspicion for measles is a priority.