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Volume 18, Number 11—November 2012

Research

Litchi–associated Acute Encephalitis in Children, Northern Vietnam, 2004–2009

Juliette Paireau, Nguyen Hai Tuan, Rémi Lefrançois, Matthew R. Buckwalter, Ngu Duy Nghia, Nguyen Tran Hien, Olivier Lortholary, Sylvain Poirée, Jean-Claude Manuguerra, Antoine Gessain, Matthew L. Albert, Paul T. Brey, Phan Thi Nga, and Arnaud FontanetComments to Author 
Author affiliations: Institut Pasteur, Paris, France (J. Paireau, R. Lefrançois, M.R. Buckwalter, J.-C. Manuguerra, A. Gessain, M.L. Albert, A. Fontanet); National Institute of Hygiene and Epidemiology, Hanoi, Vietnam (N.H. Tuan, N.D. Nghia, P.T. Nga, N.T. Hien); Université Paris X-Nanterre, Paris (R. Lefrançois); INSERM U818, Paris (M.R. Buckwalter, M.L. Albert); Hôpital Necker-Enfants Malades, Paris (O. Lortholary, S. Poirée); Université Paris Descartes, Paris (O. Lortholary, M.L. Albert); CNRS URA 1930, Paris (A. Gessain); Institut Pasteur, Vientiane, Lao People’s Democratic Republic (P.T. Brey); and Conservatoire National des Arts et Métiers, Paris (A. Fontanet)

Main Article

Table 1

Univariate analyses of Ac Mong encephalitis, Bac Giang Province, Vietnam, 2004–2009

Variable/category IRR (95% CI)* p value†
Mean altitude, m

<9.85

1 <0.001

9.85–16.47

1.23 (0.76–1.99)

16.47–58.56

1.35 (0.83–2.20)

>58.56

2.93 (1.88–4.56)
Presence of a river in the commune

No

1 0.996

Yes

1.00 (0.70–1.43)
Litchi surface, % commune surface

<1.49

1 <0.001

1.49–5.84

1.27 (0.75–2.15)

5.84–12.92

2.89 (1.82–4.58)

>12.92

2.73 (1.72–4.35)
Rice surface, % commune surface

<6.22

1 <0.001

6.22–24.51

0.64 (0.42–0.98)

24.51–38.42

0.61 (0.40–0.93)

>38.42

0.29 (0.17–0.48)
Forest surface, % commune surface

<0.48

1 <0.001

0.48–11.13

1.81 (1.06–3.09)

11.13–40.58

3.32 (2.00–5.48)

>40.58

4.05 (2.45–6.70)
Litchi yield, tons/km2

<157.68

1 0.083

157.68–300.02

1.18 (0.75–1.84)

300.02–503.51

0.97 (0.61–1.54)

>503.51

1.42 (0.93–2.17)
Rice yield, tons/km2

<460.00

1 0.500

460.00–500.00

0.83 (0.54–1.27)

500.00–534.15

0.78 (0.50–1.21)

>534.15

0.68 (0.43–1.08)
Pigs density, no./km2

<178.11

1

178.11–419.53

0.45 (0.29–0.69) <0.001

419.53–681.32

0.47 (0.31–0.71)

>681.32

0.29 (0.18–0.47)
Poultry density, no./km2

<1,449.79

1 <0.001

1,449.79–3,715.18

0.57 (0.38–0.85)

3,715.18–7,065.25

0.58 (0.39–0.86)

>7,065.25

0.21 (0.12–0.37)
Buffaloes density, no./km2

<11.57

1 0.050

11.57–22.85

1.91 (1.18–3.11)

22.85–35.06

1.82 (1.10–2.98)

>35.06

1.72 (1.04–2.84)
Cattle density, no./km2

<7.04

1 <0.001

7.04–49.66

0.78 (0.53–1.14)

49.66–105.12

0.43 (0.28–0.67)

>105.12

0.27 (0.16–0.44)
Mean temperature, °C
January–April

<19.23

1 0.004

19.23–20.16

0.74 (0.53–1.04)

>20.16

0.53 (0.37–0.77)
May–August

<27.88

1 <0.001

27.88–28.53

0.32 (0.21–0.49)

>28.53

0.81 (0.59–1.12)
Mean humidity, %
January–April

<82.07

1 <0.001

82.07–83.55

0.81 (0.59–1.12)

>83.55

0.32 (0.21–0.49)
May–August

<82.96

1 0.059

82.96–83.84

0.72 (0.51–1.02)

>83.84

0.68 (0.47–0.97)
Total rainfall, mm
January–April

<150

1 0.059

150–210

0.94 (0.64–1.37)

>210

1.38 (0.98–1.96)
May–August

<518

1 0.059

518–636

1.38 (0.98–1.96)

>636

1.94 (0.64–1.37)

*IRR, incidence rate ratio.
†Indicates global p value.

Main Article

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