Table 1.
Detailed seropositivity statistics for dengue, chikungunya, and West Nile viruses according to study sites. Participants are considered positive for dengue if positive for at least one serotype. Sixty participants were enrolled around each Sentinel Health Center (SHC), thirty were from near the center (urban), and thirty were distant from the center (rural).
| City | Dengue Virus | Chikungunya Virus | West Nile Virus | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Nb Positive | (%) | CI * | Nb Positive | (%) | CI * | Nb Positive | (%) | CI * | |
| Ambato Boeny | 4 | 6.7 | 1.9–11.4 | 1 | 1.7 | 0.0–4.0 | 10 | 16.7 | 7.1–26.2 |
| Ambatondrazaka | 1 | 1.7 | 0.0–4.0 | 0 | 0.0 | 0.0–0.1 | 1 | 1.7 | 0.0–4.0 |
| Ambositra | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 |
| Andalatanosy | 2 | 3.3 | 0.0–8.1 | 1 | 1.7 | 0.0–4.0 | 11 | 18.3 | 16.0–20.7 |
| Anjozorobe | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 |
| Antsohihy | 4 | 6.7 | 1.9–11.4 | 7 | 11.7 | 0.0–23.6 | 18 | 30.0 | 6.2–53.8 |
| Antananarivo | 1 | 1.7 | 0.0–4.0 | 0 | 0.0 | 0.0–0.1 | 1 | 1.7 | 0.0–4.0 |
| Antsirabe | 0 | 0.0 | 0.0–0.1 | 1 | 1.7 | 0.0–4.0 | 1 | 1.7 | 0.0–4.0 |
| Antsiranana | 7 | 11.7 | 4.5–18.8 | 8 | 13.3 | 0.0–27.6 | 3 | 5.0 | 0.0–12.1 |
| Belon’i Tsiribihina | 3 | 5.0 | 0.0–12.1 | 0 | 0.0 | 0.0–0.1 | 6 | 10.0 | 5.2–14.8 |
| Ejeda | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 | 2 | 3.3 | 0.0–8.1 |
| Farafangana | 4 | 6.7 | 0.0–16.2 | 37 | 61.7 | 59.3–64.0 | 15 | 25.0 | 17.9–32.1 |
| Fianarantsoa | 0 | 0.0 | 0.0–0.1 | 1 | 1.7 | 0.0–4.0 | 2 | 3.3 | 0.0–8.1 |
| Ihosy | 3 | 5.0 | 0.0–12.1 | 0 | 0.0 | 0.0–0.1 | 20 | 33.3 | 23.8–42.9 |
| Maevatanana | 0 | 0.0 | 0.0–0.1 | 0 | 0.0 | 0.0–0.1 | 11 | 18.3 | 6.4–30.2 |
| Mahajanga | 1 | 1.7 | 0.0–4.0 | 8 | 13.3 | 3.8–22.9 | 6 | 10.0 | 5.2–14.8 |
| Mananjary | 9 | 15.0 | 0.0–31.7 | 22 | 36.7 | 8.1–65.3 | 4 | 6.7 | 1.9–11.4 |
| Mandritsara | 0 | 0.0 | 0.0–0.1 | 1 | 1.7 | 0.0–4.0 | 2 | 3.3 | 0.0–8.1 |
| Miandrivazo | 1 | 1.7 | 0.0–4.0 | 0 | 0.0 | 0.0–0.1 | 15 | 25.0 | 22.6–27.4 |
| Moramanga | 2 | 3.3 | 0.0–8.1 | 0 | 0.0 | 0.0–0.1 | 9 | 15.0 | 12.6–17.4 |
| Morombe | 1 | 1.7 | 0.0–4.0 | 0 | 0.0 | 0.0–0.1 | 5 | 8.3 | 0.0–20.2 |
| Morondava | 3 | 5.0 | 2.6–7.4 | 2 | 3.3 | 0.0–8.1 | 3 | 5.0 | 0.0–12.1 |
| Nosy Be | 29 | 48.3 | 26.9–69.8 | 52 | 86.7 | 81.9–91.4 | 14 | 23.3 | 4.2–42.4 |
| Sambava | 1 | 1.7 | 0.0–4.0 | 46 | 76.7 | 52.8–100.0 | 2 | 3.3 | 0.0–8.1 |
| Taolagnaro | 4 | 6.7 | 1.9–11.4 | 0 | 0.0 | 0.0–0.1 | 11 | 18.3 | 1.6–35.0 |
| Toamasina | 26 | 43.3 | 30.4–56.2 | 42 | 70.0 | 0.0–0.1 | 27 | 45.0 | 0.5–19.5 |
| Toliary | 2 | 3.3 | 0.0–8.1 | 1 | 1.7 | 0.0–4.0 | 6 | 10.0 | 5.2–14.8 |
| Tsiroanomandidy | 2 | 3.3 | 0.0–8.1 | 0 | 0.0 | 0.0–0.1 | 9 | 15.0 | 3.1–26.9 |
| TOTAL | 110 | 6.5 | 3.2–9.9 | 230 | 13.7 | 6.5–20.9 | 214 | 12.7 | 9.0–16.5 |
* Adjusted for clustering effect on the 56 sites. In sites where no samples tested positive, one-sided 97.5% confidence intervals were estimated using an exact unadjusted method.