Table 3.
Bivariate analysis of the meteorological factors associated with influenza activity in Kenya, January 2007–December 2013
| Association with the onset of influenza activity | Absolute association with influenza activity | |||
|---|---|---|---|---|
| Odds Ratio (95% CI) | P‐value | Incidence Rate Ratio (95% CI) | P‐value | |
| Year | 0·233a | <0·001a | ||
| 2007 | 0·70 (0·23–2·15) | 0·538 | 0·45 (0·37–0·55) | <0·001 |
| 2008 | 0·74 (0·30–1·84) | 0·516 | 0·78 (0·64–0·94) | 0·010 |
| 2009 | 0·34 (0·10–1·18) | 0·089 | 0·79 (0·62–1·00) | 0·048 |
| 2010 | 0·31 (0·07–1·36) | 0·120 | 0·96 (0·79–1·16) | 0·649 |
| 2011 | Ref | Ref | ||
| 2012 | 0·99 (0·46–2·11) | 0·979 | 0·60 (0·49–0·74) | <0·001 |
| 2013 | 0·42 (0·14–1·27) | 0·125 | 0·69 (0·56–0·85) | <0·001 |
| Week | 0·98 (0·97–1·00) | 0·123 | 1·00 (0·99–1·00) | 0·285 |
| Site | 0·813a | <0·001a | ||
| St. Elizabeth Hospital | Ref | Ref | ||
| Tabitha Clinic (Kibera) | 1·52 (0·56–4·12) | 0·410 | 1·70 (1·36–2·11) | <0·001 |
| Nyeri CRH | 0·75 (0·19–2·85) | 0·667 | 0·83 (0·64–1·08) | 0·169 |
| Kakamega CRH | 1·00 (0·30–3·37) | 1·000 | 1·07 (0·83–1·36) | 0·609 |
| Nakuru CRH | 1·13 (0·39–3·30) | 0·825 | 0·77 (0·61–0·97) | 0·025 |
| Siaya CRH | 1·10 (0·35–3·41) | 0·871 | 0·67 (0·53–0·85) | 0·001 |
| Dadaab refugee camp | 1·44 (0·37–5·57) | 0·594 | 0·94 (0·73–1·22) | 0·649 |
| Kakuma refugee camp | 1·05 (0·38–2·94) | 0·924 | 0·88 (0·71–1·09) | 0·238 |
| Kilifi County Referral Hospital | 0·49 (0·15–1·66) | 0·253 | 0·25 (0·19–0·33) | <0·001 |
| Temperature (°C) | ||||
| No lag | 0·99 (0·93–1·05) | 0·682 | 0·97 (0·95–0·98) | <0·001 |
| Lag 1 week | 0·98 (0·92–1·04) | 0·484 | 0·96 (0·95–0·98) | <0·001 |
| Lag 2 weeks | 0·97 (0·91–1·04) | 0·350 | 0·96 (0·95–0·98) | <0·001 |
| Lag 3 weeks | 0·97 (0·91–1·04) | 0·346 | 0·96 (0·95–0·98) | <0·001 |
| Lag 4 weeks | 0·97 (0·91–1·04) | 0·394 | 0·96 (0·95–0·98) | <0·001 |
| Specific humidity (g/kg) | ||||
| No lag | 0·86 (0·75–0·98) | 0·031 | 0·86 (0·84–0·89) | <0·001 |
| Lag 1 week | 0·82 (0·71–0·94) | 0·004 | 0·85 (0·83–0·88) | <0·001 |
| Lag 2 weeks | 0·84 (0·73–0·96) | 0·013 | 0·85 (0·82–0·87) | <0·001 |
| Lag 3 weeks | 0·89 (0·78–1·02) | 0·108 | 0·84 (0·82–0·87) | <0·001 |
| Lag 4 weeks | 0·86 (0·75–0·99) | 0·035 | 0·84 (0·82–0·86) | <0·001 |
| Accumulated rainfall (mm) | ||||
| No lag | 1·00 (0·99–1·01) | 0·807 | 1·00 (1·00–1·00) | 0·360 |
| Lag 1 week | 0·99 (0·98–1·00) | 0·115 | 1·00 (1·00–1·00) | 0·268 |
| Lag 2 weeks | 1·00 (1·00–1·01) | 0·409 | 1·00 (1·00–1·00) | 0·074 |
| Lag 3 weeks | 1·00 (0·99–1·01) | 0·677 | 1·00 (1·00–1·00) | 0·138 |
| Lag 4 weeks | 1·00 (0·99–1·01) | 0·811 | 1·00 (1·00–1·00) | 0·106 |
| Presence of cold–dry conditionsb | ||||
| No lag | 8·17e‐06 (0–) | 0·295 | 1·65 (1·09–2·50) | 0·019 |
| Lag 1 week | 8·17e‐06 (0–) | 0·295 | 2·05 (1·10–3·83) | 0·024 |
| Lag 2 weeks | 8·17e‐06 (0–) | 0·295 | 1·58 (0·98–2·53) | 0·059 |
| Lag 3 weeks | 8·17e‐06 (0–) | 0·295 | 2·12 (1·13–4·01) | 0·020 |
| Lag 4 weeks | 8·18e‐06 (0–) | 0·319 | 1·25 (0·74–2·11) | 0·401 |
a
Overall P‐value.
b
Cold–dry periods were defined as weeks when the average temperature was <18°C and specific humidity was <11 g/kg.