Dengue IgG Seropositivity Signals Ongoing Arboviral Exposure in Chabahar
Serologic evidence from Chabahar city points to established dengue exposure in a community where Aedes aegypti has already taken hold and local transmission has been reported since 2023. In 650 serum samples collected from January to February 2025 across the catchment area of eight health centers, ELISA testing found an overall dengue IgG seropositivity of 14.3% and chikungunya IgG seropositivity of 0.9%. Those numbers do not describe acute illness in real time; they map prior infection and reveal how deeply arboviral transmission has already reached into the population. The signal is especially important in a city positioned along the epidemiologic edge of spread, where mosquito ecology can shift quickly from imported risk to sustained local circulation.
One sentence captures the public health tension here: prior dengue exposure is no longer rare in Chabahar.
The pattern was not uniform across the city. Seroprevalence reached 25% in the urban Zibashahr and urban-2 districts, while Kambel Soleiman showed the lowest prevalence at 4%. Such geographic clustering fits the biology of mosquito-borne transmission, where local breeding sites, housing density, human movement, and vector abundance can create narrow hot spots of infection rather than a flat citywide distribution. In practice, a district with more abundant Aedes mosquitoes can accumulate exposure even when neighboring areas remain comparatively less affected, a reminder that arboviral control rarely succeeds through broad messaging alone. It requires targeted source reduction, larval control, and surveillance that follows the mosquito as closely as it follows the patient.
Demographic differences sharpened the picture. Men had higher dengue seroprevalence than women, 17% versus 10.8%, with a statistically significant difference (_p_ = 0.012). Seropositivity also fell as educational attainment rose (_p_ = 0.021), and older age was associated with increased dengue IgG positivity (_p_ = 0.040). These associations may reflect cumulative exposure over time, differences in outdoor activity, occupational or domestic mosquito contact, and uneven access to preventive measures such as screening, repellents, or mosquito-proof housing. Age-associated seropositivity makes biological sense because IgG records an exposure history that accumulates with repeated bites and repeated viral encounters; in an endemic or emerging setting, older adults often carry the imprint of longer environmental risk. The educational gradient suggests that risk is also social, not merely entomologic.
Occupation did not show a significant association with dengue seropositivity, and self-reported mosquito bite exposure did not correlate significantly with serologic status. Neither finding should be read as reassuring. Self-report is a blunt instrument for vector exposure, and mosquito bites are easy to underestimate, especially in settings where bites occur outdoors, at dusk, or during routine daily activity. Serology is often more reliable than recall in reconstructing transmission intensity because antibodies retain the memory of prior infection long after the fever, rash, or arthralgia has passed. In that sense, the ELISA results function as a population archive of exposure rather than a simple snapshot of illness.
Chikungunya activity appeared limited in this survey, with IgG positivity at 0.9%. Low seroprevalence does not exclude future spread, particularly in a region already suitable for Aedes transmission. It does, however, suggest that dengue has moved further along the local transmission curve than chikungunya, at least at the time of sampling. Different arboviruses can enter the same ecological setting at different speeds depending on seeding events, human mobility, and the intensity of vector contact. For clinicians and public health teams, the low chikungunya seropositivity should not encourage complacency; it should reinforce the value of layered surveillance before the virus gains the same foothold now visible for dengue.
District-Level Hot Spots Point to Vector Control Priorities
The strongest operational message comes from the district variation. A seroprevalence of 25% in selected urban areas indicates concentrated transmission pressure, not a diffuse background nuisance. When infection risk concentrates in a few neighborhoods, vector control can be focused where it may do the most good: breeding-site elimination, household inspections, community engagement, and intensified entomologic monitoring in the highest-risk zones. Chabahar’s urban districts may also serve as warning sites for nearby communities if vector density and human movement remain unchecked. Control measures that ignore these hot spots will likely miss the local conditions driving transmission.
The study also places Chabahar in a broader regional context. The establishment of Aedes aegypti and the report of local dengue transmission since 2023 mean the city has crossed a threshold from vulnerability to documented circulation. Once local transmission is established, the goal shifts from preventing introduction to suppressing amplification. Seroprevalence data are especially useful at that stage because they can reveal hidden spread that is not captured by symptomatic case counts alone. Mild infections, misdiagnosed febrile illnesses, and asymptomatic infections all leave gaps in routine surveillance; antibody testing helps close them.
At the bedside, the findings matter because dengue recognition in newly affected areas is often delayed. Fever, myalgia, headache, and rash can be mistaken for other common infections, and chikungunya can complicate the clinical picture when it does appear. Local clinicians in Chabahar and similar coastal settings need a low threshold for considering arboviral disease during febrile seasons, particularly when the patient comes from a district with documented higher seropositivity. Public health teams, meanwhile, need to treat serology as a tool for mapping risk rather than as a retrospective academic exercise.
The survey also has limits inherent to cross-sectional serology. IgG positivity indicates previous exposure, not necessarily recent infection, and ELISA cannot specify exactly when transmission occurred. The data describe one window between January and February 2025, so they cannot capture seasonal swings or year-to-year volatility. Even so, the findings are difficult to dismiss: dengue exposure is clearly established in the general population of Chabahar, and the clustering in urban districts argues for intensified surveillance where mosquito density is highest. The next question is not whether arboviral risk exists there; it is how fast local control can outpace the ecology that is already sustaining it.