Background: Acute febrile illnesses remain a major diagnostic challenge in tropical regions where malaria and arboviral infections coexist. This study assessed the prevalence and interaction of Plasmodium falciparum and arbovirus infections among febrile patients in Gabon.

Methods: A total of 524 patients presenting with acute fever were enrolled. Demographic, clinical, and biological data were collected. Malaria diagnosis was performed by microscopy, and arboviral infections (Zika, dengue, and chikungunya viruses) were screened using rapid diagnostic tests (RDTs).

Results: The median age of participants was 60 months. Malaria prevalence was 38.0% (199/524), with P. falciparum as the sole species detected. Arbovirus RDT positivity was observed in 39.1% (205/524) of cases, mainly due to recent Zika virus infection (35.1%; 184/524), while dengue and chikungunya IgM seropositivity rates were 8.0% (42/524) and 0.6% (3/524), respectively. Suspected coinfections were frequent (21.2%), predominantly P. falciparumZika virus (17.3%; 39/225). Parasite density was significantly higher in coinfected patients (p < 0.01). Coinfection was associated with lower haemoglobin levels (p = 0.03) and a higher risk of thrombocytopenia (p < 0.01). Older age and absence of insecticide-treated net use were significant risk factors (p < 0.05). Arboviral seropositivity increased with age and was highest among urban residents, whereas malaria was more prevalent in rural areas.

Conclusion: The coexistence of malaria and arboviral infections is common among febrile patients in Gabon, with coinfection associated with haematological alterations and higher parasite loads. These findings highlight the need for integrated diagnostic approaches and improved vector control strategies in endemic settings.