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Table 3 Incidence Rate Ratios (IRR) and 95% confidence intervals of acute respiratory symptoms (ARS) for each eruptive month(s) (reference = previous year’s same month(s)) for all health facilities and according to their distance from Nyiragongo. Values of n concern the numbers of health centres and values in italics indicate the IRR with significant p values for the comparison with the overall IRR

From: Respiratory health and eruptions of the Nyiragongo and Nyamulagira volcanoes in the Democratic Republic of Congo: a time-series analysis

Eruption

Date

IRR ≤ 26 km

(n = 17)

IRR > 102 km

(n = 21)

IRR overall

(n = 78)

Nyamulagira

2001, 6th Feb to 5th May

Jan - May 1999

1

1

1

Dec 2000

1.8 [0.9–3.7]

1.0 [0.6–1.7]

1.4 [1.1–1.9]

Jan 2001

1.9 [1.0–3.5]

0.9 [0.7–1.3]

1.3 [1.0–1.6]

Feb - Apr 2001

1.4 [0.8–2.6]

0.9 [0.6–1.2]

1.2 [1.0–1.5]

May 2001

1.4 [0.7–2.8]

0.8 [0.5–1.1]

1.2 [1.0–1.5]

Nyiragongo

2002, 17th Jan

Nov 2000 - Feb 2001

1

1

1

Nov 2001

1.3 [0.9–2.0]

0.9 [0.5–1.4]

1.3 [1.1–1.5]

Dec 2001

1.2 [0.8–1.8]

1.0 [0.7–1.5]

1.3 [1.1–1.5]

Jan 2002

4.9 [2.3-10.7]

1.9 [1.2–3.3]

2.1 [1.4–3.2]

Feb 2002

5.8 [2.4–13.9]

2.1 [1.2–3.7]

2.3 [1.5–3.6]

Nyamulagira

2002, July to Sept

May - Oct 2001

1

1

1

May 2002

2.8 [1.4–5.4]

2.1 [1.2–3.8]

1.7 [1.3–2.2]

June 2002

1.6 [0.9–3.1]

1.8 [1.0–3.2]

1.4 [1.1–1.7]

July - Sept 2002

2.6 [0.9–7.2]

1.5 [0.8–2.9]

1.6 [1.2–2.3]

Oct 2002

1.8 [1.0–3.2]

1.8 [1. 0–3.1]

1.5 [1.2–1.8]

Nyamulagira

2006, 27th Nov to 5th Dec

Oct 2005 - Feb 2006

1

1

1

Oct 2006

0.9 [0.7–1.1]

1.4 [1.0–1.9]

1.1 [0.9–1.3]

Nov 2006

1.1 [0.9–1.4]

1.6 [1.1–2.4]

1.3 [1.0–1.6]

Dec 2006

1.1 [0.9–1.5]

1.4 [1.0–2.0]

1.3 [1.0–1.7]

Jan 2007

2.1 [1.6–2.6]

2.2 [1.4–3.3]

1.8 [1.4–2.4]

Feb 2007

1.5 [1.0–2.2]

1.9 [1.3–2.8]

1.7 [1.3–2.1]

Nyamulagira

2010, 2nd to 27th Jan

Nov 2008 - Feb 2009

1

1

1

Nov 2009

0.4 [0.2–0.7]

0.8 [0.6–1.1]

1.1 [0.8–1.5]

Dec 2009

0.3 [0.2–0.7]

0.8 [0.6–1.0]

0.9 [0.7–1.3]

Jan 2010

0.2 [0.1–0.3]

0.8 [0.6–1.0]

0.7 [0.6–1.1]

Feb 2010

0.3 [0.2–0.4]

0.9 [0.7–1.3]

0.7 [0.5–0.9]