Fig 1.
Illustration of the steps and potential pathways from being exposed to the pathogen reservoir to detection of disease.
The red (blue) taps and swimmers represent contaminated (uncontaminated) drinking and recreational water. The red (blue) silhouette represents infected (not-infected) humans. Here and throughout, any kind of environment-containing pathogens that can serve as a medium for transmission (e.g. drinking water, sewage system) is referred to as “pathogen reservoir”; any form of direct or indirect contact with such medium, irrespective of the presence of the pathogen, is referred to as an “exposure”. According to this conceptual scheme, a disease-free situation is the combination of negligible pathogen population in, and/or negligible exposure of susceptible individuals to, the pathogen reservoir. Infections arise from increased interactions of exposed susceptibles with the pathogen reservoir. This can be caused by a growth in the pathogen population (driven, for example, by temperature) and/or larger exposure to the pathogen. An increase in the exposure can be directly or indirectly driven by meteorological/climate variables (e.g. high temperature increasing the risk of drinking contaminated water), environmental causes (e.g. poor water drainage management due to land use), and behavioural and/or socio-economic factors (e.g. recreational activity in unclean water). Changes in the population of susceptibles (for example due to immigration, loss of immunity and/or human-to-human transmission) can alter the patterns of exposure.
Table 1.
Organisms causing diseases related to water (excluding vector borne diseases).
The symbol ● specifies the known routes of transmission (not exclusively); (●) specifies the probable route of transmission but no direct evidence available. The last column indicates which organism is classified as Neglected Tropical disease, according to the World Health Organisation (W) [2], the Centers for Disease Control and Prevention (C) [3], and the journal PLOS Neglected Tropical Diseases (P) [4]. The different routes of transmission are: A) Drinking water borne; B) Water washed (reduced water access); C) Water based; D) Foodborne through water; E) Water infecting wounds; F) Bathing water transmission; G) Respiratory waterborne; H) Toxic poisoning through a bloom; I) Infection or disease related to damp; J) Medical water or solutions.
Table 2.
List of scientific questions and related notes.
Fig 2.
Flow chart describing the selection process of all abstracts.
Fig 3.
Proportion of papers investigating a particular pathogen or disease.
Fig 4.
(a) Distribution of countries for which water-associated disease data were the focus of the reviewed papers (b) Geographic distribution of the 7 most commonly studied water-associated pathogens (resulting either in an epidemic or endemic situations) which were the focus of the reviewed papers.
Each circle refers to specific countries, In particular, the largest circle in Asia, refers to Bangladesh.
Fig 5.
Each dot corresponds to a reviewed paper; the brown bubbles correspond to the keywords describing the techniques. A connection between a paper and a keyword occurs when the related technique is used. The size of the bubble increases (logarithmically) with the number of papers citing the keyword. For visual purpose only, i) the bubbles are displayed with different shades of brown and ii) the technical keywords (listed in S1 Table in the Supporting Information) describing methods used by only one paper are not displayed (the full set is shown in S1 Fig in the Supporting Information). The graph was produced by using the i-graph package[13] in R.
Fig 6.
The most common, general methods used in the reviewed papers (listed in S1 Table in the supporting information).
Table 3.
Discussion of some key features of the general methods and their relevance to the investigation of the effect of weather and/or climate change.
Fig 7.
The most common environmental and socio-economic variables included in the reviewed papers.