Malaria-Dengue Co-Infection among Febrile Inpatients in Peshawar: Prevalence, Species Distribution, and Risk Factors.

Abstract

Objective: To determine the prevalence and species distribution of malaria among febrile inpatients, document the co-infection burden, assess severe malaria by World Health Organisation (WHO) criteria, and identify risk factors for malaria positivity.

Study design: An analytical cross-sectional study. Place and Duration of the Study: Department of Internal Medicine, Hayatabad Medical Complex and Khyber Girls Medical College, Peshawar, Pakistan, from January 2024 to December 2025.

Methodology: Febrile patients were screened using blood smear microscopy and rapid diagnostic testing (RDT). Severe malaria was defined according to WHO criteria. Co-infection was confirmed by dengue non-structural protein 1 (NS1) antigen and immunoglobulin M (IgM) serology, chikungunya IgM serology, and blood culture for Salmonella Typhi. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using binary logistic regression (SPSS version 26.0).

Results: Of 5,022 febrile patients screened, 81 (1.61%) were malaria-positive. Plasmodium (P.) vivax accounted for 58 (71.60%), P. falciparum for 19 (23.46%), and mixed P. vivax /P. falciparum infection for 4 (4.94%). Nine (11.1%) met WHO severe malaria criteria, mostly severe anaemia (5/9). Concurrent confirmed infection was present in 35 (43.2%): dengue in 18 (22.2%), chikungunya in 8 (9.9%), typhoid fever in 7 (8.6%), and other pathogens in 2 (2.5%). Male gender (OR 1.78, 95% CI 1.13-2.81; p = 0.014) and monsoon season (OR 2.02, 95% CI 1.24-3.31; p = 0.005) were significant risk factors.

Conclusion: P. vivax was the dominant species. Concurrent confirmed infection was present in more than two in every five malaria- positive inpatients, with dengue infection present in nearly one in four. Mixed Plasmodium infection was uncommon but was still observed. Routine parallel screening is warranted in febrile patients in the studied geographical area.

Key words: Malaria, Dengue, Co-infection, Plasmodium vivax, Plasmodium falciparum, Febrile illness, Risk factors, Species distribution.