Table 5 Sub-group analysis based on annual precipitation, humidity, annual rainfall, average temperature, WHO regions, income level, mean age, and diagnostic method in included cross-sectional studies
Variables | No studies | Sample size | Infected | Pooled prevalence (95% CI) | Heterogeneity | ||
|---|---|---|---|---|---|---|---|
| Â | I2 | Ï„2 | p-value | ||||
Annual precipitation | |||||||
  < 300 | 27 | 8820 | 1720 | 0.270 (0.192–0.355) | 98 | 0.057 | p < 0.001 |
 300–650 | 2 | 526 | 179 | 0.243 (0.006–0.655) | 98 | 0.093 | p < 0.001 |
 651–1000 | 8 | 9639 | 1668 | 0.234 (0.119–0.372) | 97 | 0.049 | p < 0.001 |
  > 1000 | 3 | 1009 | 153 | 0.239 (0.000–0713) | 99 | 0.188 | p < 0.001 |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Humidity (%) | |||||||
  < 40 | 17 | 3629 | 1117 | 0.303 (0.218–0.394) | 97 | 0.039 | p < 0.001 |
 40–75 | 16 | 14,224 | 2181 | 0.240 (0.151–0.342) | 98 | 0.050 | p < 0.001 |
  > 75 | 7 | 2141 | 422 | 0.201 (0.033–0.459) | 99 | 0.139 | p < 0.001 |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Annual rainfall (mm) | |||||||
  < 400 | 20 | 4118 | 1369 | 0.331 (0.249–0.418) | 97 | 0.040 | p < 0.001 |
 401–1000 | 6 | 4447 | 539 | 0.315 (0.125–0.544) | 99 | 0.081 | p < 0.001 |
 1001–1500 | 11 | 10,707 | 1719 | 0.142 (0.082–0.215) | 97 | 0.024 | p < 0.001 |
  > 1500 | 3 | 722 | 93 | 0.174 (0.000–0.694) | 99 | 0.235 | p < 0.001 |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Average temperature (°C) | |||||||
  < 10 | 1 | 370 | 166 | 0.448 (0.398–0.499) | – | – | – |
 10–20 | 27 | 17,106 | 3059 | 0.263 (0.101–0.403) | 98 | 0.044 | p < 0.001 |
  > 20 | 12 | 2518 | 495 | 0.0235 (0.018- 0.106) | 98 | 0.099 | p < 0.001 |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
WHO region | |||||||
 African region | 4 | 1124 | 123 | 0.011 (0.0001–0.368) | 97 | 0.035 | p < 0.001 |
 Eastern Mediterranean Region | 20 | 4118 | 1369 | 0.331 (0.244–0.424) | 97 | 0.040 | p < 0.001 |
 European Region | 5 | 1689 | 590 | 0.386 (0.150–0.656) | 98 | 0.047 | p < 0.001 |
 Region of the Americas | 6 | 8768 | 1401 | 0.170 (0.059–0.322) | 83 | 0.025 | p < 0.001 |
 Western Pacific Region | 4 | 4150 | 234 | 0.156 (0.000–0.744) | 99 | 0.156 | p < 0.001 |
 South-East Asia Region | 1 | 145 | 3 | 0.020 (0.007–0.059) | – | – | – |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Income level | |||||||
 High income | 9 | 10,532 | 1890 | 0.219 (0.122–0.336) | 98 | 0.038 | p < 0.001 |
 Upper middle income | 6 | 4063 | 295 | 0.215 (0.049–0.452) | 98 | 0.097 | p < 0.001 |
 Lower middle income | 25 | 5399 | 1535 | 0.285 (0.201–0.378) | 98 | 0.060 | p < 0.001 |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Mean age | |||||||
 15–20 | 1 | 188 | 125 | 0.664 (0.594–0.724) | – | – | – |
 20–25 | 4 | 794 | 227 | 0.316 (0.146–0.516) | 96 | 0.041 | p < 0.001 |
 26–30 | 1 | 119 | 31 | 0.260 (0.190–0.346) | – | – | – |
 31–35 | 4 | 1210 | 150 | 0.090 (0.013–0.224) | 97 | 0.034 | p < 0.001 |
 36–40 | 4 | 975 | 156 | 0.277 (0.135–0.445) | 95 | 0.036 | p < 0.001 |
 41–45 | 5 | 1394 | 268 | 0.250 (0.039–0.558) | 99 | 0.103 | p < 0.001 |
 46–50 | 2 | 215 | 11 | 0.056 (0.0004–0.174) | 86 | 0.061 | p < 0.001 |
 Total | 21 | 4895 | 968 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |
Diagnostic method | |||||||
 Direct smear & Sedimentation | 7 | 2001 | 284 | 0.141 (0.051–0.265) | 98 | 0.042 | p < 0.001 |
 Direct smear & Sedimentation & Stain | 8 | 1522 | 463 | 0.349 (0.241–0.465) | 95 | 0.026 | p < 0.001 |
 Direct smear & PCR | 1 | 113 | 80 | 0.708 (0.618–0.783) | – | – | – |
 Direct smear | 1 | 145 | 3 | 0.020 (0.007–0.059) | – | – | – |
 ELISA | 12 | 5819 | 1033 | 0.335 (0.214–0.468) | 99 | 0.055 | p < 0.001 |
 Direct smear & ELISA & Culture | 1 | 550 | 70 | 0.127 (0.102–0.157) | – | – | – |
 IFA | 2 | 689 | 309 | 0.443 (0.001–0.974) | 99 | 0.237 | p < 0.001 |
 Solid-phase immunoassay | 1 | 358 | 58 | 0.162 (0.127–0.203) | – | – | – |
 IFA & Sabin-Feldman dye test | 1 | 7440 | 1211 | 0.162 (0.154–0.171) | – | – | – |
 Direct smear & Culture & Stain | 1 | 341 | 67 | 0.196 (0.157–0.241) | – | – | – |
 Direct smear & Sedimentation & Culture | 1 | 173 | 41 | 0.237 (0.179–0.305) | – | – | – |
 Direct smear & Willis | 1 | 97 | 4 | 0.041 (0.016–0.101) | – | – | – |
 EIA | 1 | 472 | 43 | 0.091 (0.068–0.120) | – | – | – |
 ELISA & PCR | 1 | 118 | 41 | 0.347 (0.267–0.437) | – | – | – |
 Ritchie's modified method & Lutz | 1 | 156 | 13 | 0.083 (0.049–0.137) | – | – | – |
 Total | 40 | 19,994 | 3720 | 0.252 (0.189–0.320) | 98 | 0.063 | p < 0.001 |