Editing IPCC:AR6/WGII/Chapter-9 (section)

==== 9.10.2.2 Diarrhoeal Diseases, HIV and Other Infectious Diseases ====

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===== 9.10.2.2.1 Diarrhoeal diseases =====

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Observed impacts

Africa has the highest rates of death due to diarrhoeal diseases in the world ( [[#Havelaar--2015|Havelaar et al., 2015]] ; [[#Troeger--2018|Troeger et al., 2018]] ) and many children have repeated diarrhoeal episodes with impaired growth, stunting, immune dysfunction and reduced cognitive performance ( [[#Squire--2017|Squire and Ryan, 2017]] ). High land and sea temperatures ( [[#Paz--2009|Paz, 2009]] ; [[#Musengimana--2016|Musengimana et al., 2016]] ) and precipitation extremes increase transmission of bacterial and protozoal diarrhoeal disease agents ( [[#Boeckmann--2019|Boeckmann et al., 2019]] ) through contamination of drinking water and food preparation and preservation practices (Figure 9.33; [[#Levy--2016|Levy et al., 2016]] ; [[#Soneja--2016|Soneja et al., 2016]] ; [[#Walker--2018|Walker, 2018]] ).

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'''Figure 9.33 |''' '''Schematic showing the pathways to diarrhoeal disease impacts in Africa as a result of exposure to climate hazards.''' Numbers in the figure refer to chapter sections of this report.

Cholera incidence has been shown to increase with temperature ( [[#Trærup--2011|Trærup et al., 2011]] ). Outbreaks, however, are most frequent in east and southern Africa following tropical cyclones ( [[#Moore--2017b|Moore et al., 2017b]] ; [[#Troeger--2018|Troeger et al., 2018]] ; [[#Ajayi--2019|Ajayi and Smith, 2019]] ; [[#Cambaza--2019|Cambaza et al., 2019]] ).

Africa’s rapidly urbanising population increases the demand for freshwater and is occurring in places that already have stretched water and sanitation infrastructure ( [[#Howard--2016|Howard et al., 2016]] ). These conditions, especially during periods of water scarcity, can reduce the frequency and adequacy of hand washing and thereby increase disease transmission.

Projected risks

Disruptions in water availability, such as during droughts or infrastructure breakdown, will jeopardise access to safe water and adequate sanitation, undermine hygiene practices and increase environmental contamination with toxins ( [[#Howard--2016|Howard et al., 2016]] ; [[#WWF-SA--2016|WWF-SA, 2016]] ; [[#Miller--2017|Miller and Hutchins, 2017]] ).

Climate change is projected to cause 20,000–30,000 additional diarrhoeal deaths in children (&lt;15 years old) by mid-century under 1.5°C–2.1°C global warming ( [[#WHO--2014|WHO, 2014]] ), with west Africa most affected, followed by east, central and southern Africa. Cholera outbreaks are anticipated to impact east Africa most severely during and particularly after ENSO events ( [[#Moore--2017b|Moore et al., 2017b]] ).

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===== 9.10.2.2.2 HIV =====

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Observed impacts

Although levels of new HIV infections declined sharply during the last decade, still more than a million adults and children become infected each year ( [[#UNAIDS--2020|UNAIDS, 2020]] ). Climate influences on HIV are predominately indirect such as through heightened migration due to climate variability, or extreme weather events leading to increased transactional sex to replace lost sources of income. Changes in climate affect each of the main drivers of HIV transmission in women, including poverty, inequity and gender-based violence ( [[#Burke--2015a|Burke et al., 2015a]] ; [[#Loevinsohn--2015|Loevinsohn, 2015]] ; [[#Fiorella--2019|Fiorella et al., 2019]] ).

Projected risks

‘Oscillating’ or ‘circular’ migration for migrant workers in urban and mining centres drove HIV transmission in the 1990s and 2000s ( [[#Lurie--2006|Lurie, 2006]] ), and climate-related displacement may have similar effects (See Box 9.7; [[#Gray--2012|Gray and Mueller, 2012]] ; [[#Loevinsohn--2015|Loevinsohn, 2015]] ; [[#Low--2019|Low et al., 2019]] ). Food insecurity and nutritional deficiencies, projected to increase with increasingly variable climates, has been shown to increase sexual risk-taking and migration, as well as increase susceptibility to other infections ( [[#Lieber--2021|Lieber et al., 2021]] ). Projected increases in exposure to infectious diseases pose considerable threats to HIV-infected people who may already have compromised immune function. Additionally, reduced lung function in people with HIV from previous tuberculosis infection may put them at high risk for morbidity and death during extreme heat ( [[#Abayomi--2014|Abayomi and Cowan, 2014]] ). Moreover, extreme weather events accompanied by damage to health system infrastructure could compromise the continuity of antiretroviral treatment ( [[#Weiser--2010|Weiser et al., 2010]] ; [[#Pozniak--2020|Pozniak et al., 2020]] ).

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===== 9.10.2.2.3 Other infectious diseases =====

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Poor populations in the western Sahel have the highest burden of bacterial meningitis worldwide, with seasonal dynamics driven by the dry Harmattan winds that transport dust long distances across the continent ( [[#Agier--2013|Agier et al., 2013]] ; [[#García-Pando--2014|García-Pando et al., 2014]] ). In Nigeria, rising temperatures are projected to increase meningitis cases by about 50% for 1.8°C global warming (RCP2.6 in 2060–2075), and by almost double for 3.4°C global warming (RCP8.5 in 2060–2075) ( [[#Abdussalam--2014|Abdussalam et al., 2014]] ). Bilharzia is also highly climate sensitive, with its distribution influenced by changes in temperature and precipitation, as well as development, such as the introduction of freshwater projects (e.g., canals, hydroelectric dams and irrigation schemes) ( [[#Adekiya--2019|Adekiya et al., 2019]] ).

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'''Figure 9.34 |''' '''Schematic showing the pathways of impact for heat-related morbidities in Africa as a result of exposure to climate hazards.''' Numbers in the figure refer to chapter sections of this report. Indirect health impacts of heat are not shown. For example, risk of malnutrition from reduced crop yields or reduced fisheries catches (see [[#9.8.5|Section 9.8.5]] ).

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