iii) Climate change would lead to severe risks of morbidity and mortality caused by waterborne diseases, particularly for diarrhoea in children in many lower- and middle-income countries  and where vulnerability remains high . The global CMR for diarrhoea is 1.98 for all ages, but varies by region and age group, reaching as high as 53 for <1-year-olds in Africa . In these vulnerable populations, even a small percentage increase can lead to substantial additional morbidity and mortality. For example, assuming no change in vulnerability or population, an increase in diarrhoea mortality of only 5% over 2019 baseline rates would create a severe risk  for children under the age of 1 in the World Health Organization  Africa  region. This percent increase due to climate change is plausible since diarrhoea incidence increases of 7%  are associated with a 1°℃ increase in ambient temperature , and diarrhoea is positively associated with heavy rainfall and flooding events , expected in some regions . Assuming vulnerability remains the same as today, mortality and morbidity rates would increase equivalently.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report