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. 2019 Sep;101(3):521-524.
doi: 10.4269/ajtmh.18-1016.

Associations between Public Awareness, Local Precipitation, and Cholera in Yemen in 2017

Shi Zhao  1   2 , Salihu S Musa  2 , Jing Qin  1 , Daihai He  2
Affiliations

Associations between Public Awareness, Local Precipitation, and Cholera in Yemen in 2017

Shi Zhao et al. Am J Trop Med Hyg. 2019 Sep.

Abstract

In 2017-18, a large-scale cholera outbreak swept Yemen. We calculated the number of culture-confirmed cases from the suspected cases and diagnosis testing records. We estimate 184,248 confirmed cholera cases between April 2017 and the end of 2017, and the reproduction number of 2.2 with 95% CI of [2.1, 2.3] during the initial stage. We find a significantly (nonlinear) positive association between the reproduction number (R t) and precipitation, explained 13% of transmissibility changes, with one unit (mm) increment in precipitation leading to an increment of 20.1% in R t. We find a significantly (nonlinear) negative association between the R t and cumulative Google Trends index (GTI), explained 62% of transmissibility changes, with one unit increment in cumulative GTI leading to a drop of 0.03% in R t.

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Figures

Figure 1.
Figure 1.
The cholera diagnosis testing records, cases, estimated transmissibility of the 2nd (the major) epidemic wave, and precipitation in Yemen, from 2017 to July 2018. (A) Cholera rapid diagnostic test (rapid diagnostic test, green circles and curve), and culture-based test (blue diamonds and curve) positive rates (%); the vertical bars are the 95% CI; and the size of dots indicates the diagnosis testing sample sizes. (B) The weekly number of suspected (gray) and the point estimates of the confirmed (black) cholera cases. (C) The estimated instantaneous transmissibility in term of reproduction number (Rt) in 2017; and the vertical bars are the 95% CIs. (D) The daily average precipitation (daily reported, dots, and moving-average, bars, unit: mm) of Yemen in 2017. Note that (A)–(E) share the same horizontal axis. (E) The Google Trends index (GTI) of the term “cholera” of Yemen in 2017, and its cumulative (cum.) sum. (F) The estimated nonlinear relationship between Rt and the local precipitation (with a lag of +7 days); and the vertical bars are the 95% CIs. (G) The violin plot of the distribution of the daily reported and exponentially weighted moving-averaged precipitation; the medians are indicated by the white circles; the interquartile ranges are indicated by the black rectangles; and the purple areas display the kernel density distributions estimation (i.e., smoothed histogram). (H) The estimated nonlinear relationship between Rt and the GTI; and the vertical bars are the 95% CIs. This figure appears in color at www.ajtmh.org.
See this image and copyright information in PMC

References

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    1. Camacho A, et al. 2018. Cholera epidemic in Yemen, 2016–18: an analysis of surveillance data. Lancet Glob Health 6: e680–e690. - PMC - PubMed
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    1. The World Weather and Climate Information , 2018. The Climate and Average Weather in Yemen. The World Weather and Climate Information; Available at: https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sun.... Accessed November 29, 2018.