Seroprevalence, Environmental Risk Factors, and Seasonal Patterns of Dengue Virus Infection in Nigeria: A Systematic Review and Meta-analysis (2014-2024)

This systematic review and meta-analysis of 33 studies (2014–2024) reveals that dengue virus transmission is widespread and geographically heterogeneous across Nigeria, with significant seasonal peaks during the rainy season and strong associations with modifiable environmental risk factors such as proximity to refuse dumps, open water storage, and lack of mosquito nets.

The Gist

Imagine Nigeria as a massive, bustling city where the weather changes like a mood ring. Sometimes it's dry and dusty, and sometimes it pours rain, turning the streets into rivers. In this city, there's a tiny, invisible enemy: the Dengue Virus.

For a long time, when people in Nigeria got a high fever, doctors often assumed it was just Malaria (a very common mosquito-borne disease there). It's like if you heard a siren and immediately assumed it was a fire truck, without checking if it might be an ambulance. Because of this assumption, Dengue was hiding in plain sight, like a ghost in the machine.

This paper is like a team of detectives (the researchers) who decided to stop guessing and start counting. They gathered every single report, study, and medical record from the last 10 years (2014–2024) to answer three big questions:

1. How many people have actually caught Dengue?
2. Where are the "hotspots" where the virus is most active?
3. What in our daily lives is inviting the virus in?

Here is what they found, broken down simply:

1. The "Ghost" is Everywhere

The researchers found that Dengue isn't just a rare visitor; it's a permanent resident.

• The "Recent" Infection (IgM): About 1 in 5 people they tested had signs of a recent infection. Think of this as finding fresh footprints in the mud. It means the virus is actively walking around right now.
• The "Past" Infection (IgG): Another 1 in 5 people had signs of having caught it in the past. These are the old footprints, showing that the virus has been circulating for a long time, building up a history in the population.

2. The Geography of Danger

Not all parts of Nigeria are equally risky. It's like a game of "Hot and Cold."

• The Southeast: This region was the "hottest" zone, with the highest number of infections. It's like a campfire where the virus is burning brightest.
• The South-South: This area was the "coolest," with the lowest numbers.
• Why? The virus loves specific environments. It thrives where there is rapid city growth, poor drainage, and lots of people living close together.

3. The "Open Door" Policy (Risk Factors)

The study found that the virus doesn't just attack randomly; it targets specific habits. Imagine the virus as a burglar looking for an unlocked door. The study found four main "open doors" that let the virus in:

• The Trash Can Trap (Refuse Dumpsites): Living near a garbage dump increased the risk of infection by 9 times!
  • Analogy: Garbage piles are like all-you-can-eat buffets for mosquitoes. Rain fills old tires and plastic cups in the trash with water, creating perfect nurseries for mosquito babies. If you live next to the buffet, you're more likely to get bitten.
• The Open Water Bucket: Storing water in open containers at home doubled the risk.
  • Analogy: An open water bucket is a swimming pool for mosquitoes. If you leave the pool open, the mosquitoes will come to swim and lay eggs.
• No Net, No Sleep: People who didn't use mosquito nets were nearly 9 times more likely to get infected.
  • Analogy: A mosquito net is a shield or a force field. Without it, you are an open target in a dark room full of hungry mosquitoes.
• The Malaria Mix-up: People who had Malaria were also more likely to have Dengue.
  • Analogy: This is like finding two different thieves in the same house. It suggests that the conditions that let Malaria in (mosquitoes, poor housing) also let Dengue in. It also means doctors might be treating the wrong "thief" if they only check for Malaria.

4. The Seasonal Rhythm

The virus has a dance partner: The Rain.

• When the rainy season hits, the virus throws a party. The rain creates more puddles, more mosquitoes, and more chances for the virus to spread.
• When it's dry, the party slows down, but the virus doesn't disappear; it just waits for the next storm.

5. The Four Faces of the Virus

The virus isn't just one thing; it has four different disguises (called Serotypes 1, 2, 3, and 4).

• Analogy: Imagine the virus is a shape-shifter. If you catch one version, you might be safe from that specific one, but the other three are still out there. Worse, if you catch a second version later, your body's defense system might get confused and make the sickness worse. The study found all four disguises are currently active in Nigeria.

The Bottom Line

This paper is a wake-up call. It tells us that Dengue is not a mystery anymore; it is a widespread, established problem in Nigeria.

What needs to happen?

1. Stop guessing: Doctors need to check for Dengue, not just Malaria, when patients have fevers.
2. Close the doors: We need to cover our water buckets, manage our trash better, and use mosquito nets.
3. Watch the weather: Public health officials need to be extra ready during the rainy season.

By understanding where the virus lives and how it gets in, Nigeria can finally start fighting back effectively, turning the lights on for a disease that has been hiding in the shadows for too long.

Technical Summary

1. Problem Statement

Despite being a major global public health concern, the epidemiology of Dengue Virus (DENV) in sub-Saharan Africa, specifically Nigeria, remains poorly characterized.

• Diagnostic Confusion: In Nigeria, febrile illnesses are frequently misdiagnosed as malaria or typhoid due to overlapping clinical symptoms, leading to the underreporting of dengue.
• Data Fragmentation: Existing data is fragmented, with significant variability in diagnostic methods (serology vs. molecular), study populations, and geographic coverage.
• Knowledge Gaps: There is a lack of quantitative synthesis regarding the true burden of infection, geographic heterogeneity, seasonal transmission patterns, and specific environmental risk factors driving transmission in the Nigerian context.

2. Methodology

The study adhered to the PRISMA 2020 guidelines and was prospectively registered with PROSPERO (CRD420261328923).

• Search Strategy: A comprehensive search was conducted across six databases (PubMed, Scopus, Web of Science, EMBASE, Google Scholar, African Index Medicus) for studies published between January 2014 and August 2024.
• Eligibility Criteria:
  • Inclusion: Studies reporting laboratory-confirmed DENV infection (IgM, IgG, NS1 antigen, RT-PCR, or PRNT) in human populations within Nigeria.
  • Exclusion: Vector-only studies, non-human studies, editorials, and studies lacking laboratory confirmation.
• Data Extraction: Two independent reviewers extracted data on prevalence, sample sizes, diagnostic markers, geographic regions, and risk factors (2×2 contingency tables for odds ratios).
• Statistical Analysis:
  • Software: R (version 4.5.2) using the meta package.
  • Model: Random-effects meta-analysis was employed to account for expected heterogeneity.
  • Transformations: Freeman–Tukey double arcsine transformation was used to stabilize variance for prevalence estimates.
  • Heterogeneity: Assessed using Cochran's Q and the $I^2$ statistic.
  • Subgroup Analysis: Conducted by diagnostic marker and geographic region (North Central, Southwest, Northwest, Northeast, Southeast, South-South).
  • Risk Factors: Pooled Odds Ratios (OR) with 95% Confidence Intervals (CI) were calculated for environmental and behavioral exposures.

3. Key Contributions

• First Comprehensive Synthesis: This is the first systematic review and meta-analysis to provide marker-specific pooled prevalence estimates for dengue in Nigeria over a decade (2014–2024).
• Quantification of Burden: It moves beyond anecdotal evidence to provide statistically robust estimates of both recent (IgM) and cumulative (IgG) exposure.
• Risk Factor Identification: It quantitatively links specific modifiable environmental factors (e.g., refuse dumpsites, water storage) to dengue seropositivity, offering actionable targets for intervention.
• Geographic Stratification: The study maps transmission intensity across Nigeria's six geopolitical zones, revealing significant spatial heterogeneity.

4. Key Results

Study Selection:

• From 1,115 initial records, 33 studies met the inclusion criteria, encompassing diverse populations (febrile patients, pregnant women, HIV patients, and general community samples).

Pooled Seroprevalence (Random-Effects Model):

• IgM (Recent Infection): 20.9% (95% CI: 13.0–30.1; $I^2 = 98.6\%$).
• IgG (Past Exposure): 19.9% (95% CI: 11.6–29.7; $I^2 = 97.7\%$).
• NS1 Antigen (Acute Infection): 8.9% (95% CI: 2.2–19.4; $I^2 = 98.5\%$).
• PCR-Confirmed: 7.0% (95% CI: 1.2–16.2; $I^2 = 25.8\%$).
• Note: Significant differences were observed across diagnostic markers ($p = 0.0002$).

Geographic Variation:

• Highest Prevalence: The Southeast region showed the highest pooled prevalence for both IgM (37%) and IgG (36%).
• Lowest Prevalence: The South-South region had the lowest estimates (IgM: 8%, IgG: 9%).
• Statistical tests confirmed significant geographic heterogeneity for both IgM ($p = 0.0179$) and IgG ($p = 0.0030$).

Risk Factors (Pooled Odds Ratios):
Strong associations were found between seropositivity and the following factors:

1. Proximity to Refuse Dumpsites: OR = 9.39 (95% CI: 7.44–11.84; $I^2 = 0\%$).
2. Non-use of Mosquito Nets: OR = 8.70 (95% CI: 5.73–13.21; $I^2 = 32.0\%$).
3. Malaria Positivity: OR = 5.54 (95% CI: 3.84–7.98; $I^2 = 23.8\%$), indicating a strong diagnostic and ecological overlap.
4. Open Household Water Storage: OR = 2.18 (95% CI: 1.65–2.89; $I^2 = 0\%$).

Serotypes and Seasonality:

• Serotypes: All four DENV serotypes (DENV-1 to DENV-4) were identified. DENV-1 was most prevalent (~35%), followed by DENV-3 (30%), DENV-2 (25%), and DENV-4 (10%).
• Seasonality: Transmission intensity significantly increased during rainy seasons, correlating with enhanced vector breeding conditions.

5. Significance and Implications

• Public Health Policy: The findings confirm that dengue is endemic and widespread in Nigeria, not merely sporadic. The high seroprevalence suggests a large pool of susceptible individuals for secondary infections, raising concerns about Antibody-Dependent Enhancement (ADE) and severe disease.
• Clinical Practice: The strong correlation with malaria positivity and the high rate of misdiagnosis necessitate the integration of dengue diagnostics (e.g., NS1 or IgM/PCR) into routine febrile illness workups, particularly in high-burden regions like the Southeast.
• Vector Control: The identification of refuse dumpsites and open water storage as primary drivers suggests that integrated vector management focusing on waste management and household water containment is more critical than broad-spectrum spraying alone.
• Surveillance: The study highlights the urgent need for standardized diagnostic protocols and expanded molecular surveillance to monitor serotype shifts and viral evolution, which are currently obscured by diagnostic variability.

Limitations:
The study noted high heterogeneity ($I^2 > 97\%$) in serological data, likely due to varying assay sensitivities and study designs. Additionally, the reliance on published summary data prevented individual participant-level adjustments for confounders.

Conclusion:
Dengue virus transmission in Nigeria is a significant, underrecognized public health threat driven by environmental and behavioral factors. The study calls for a shift from malaria-centric febrile illness management to integrated arboviral surveillance and targeted, climate-informed vector control strategies.