Drought can occur over large geographical areas and impact multiple populations. Its impacts on health are closely associated with socioeconomic factors that reduce the resilience of the population. ^{9 9}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013X

Africa is affected by drought more than any other continent, and is where the majority of drought-related deaths occur. ^{10 10}The human cost of weather related disasters: 1995-2015. CRED/UNISDR, 2015X

Notable impacts on health and wellbeing are felt particularly in the following regions and countries:

• The Sahel is affected by drought affecting water supply and adding to economic stress, increasing food scarcity, livestock deaths, and population migration. ^{11 11}Wearewater.org: The Sahel, desertification beyond droughtX
• In the Horn of Africa (Ethiopia, Somalia, Eritrea and Djibouti), where almost 80% of the population is rural and highly dependent on rain-fed agriculture, drought is exacerbating poverty and increasing population migration. For example, from November 2016 to December 2017, 892,000 drought-related displacements were recorded in Somalia with 6.7 million people affected by food insecurity across the country. ^{12 12}FAO: Drought Facts; Migration and land Degradation: recent experiences in future trends.McLeman, 2017X ^{13 13}WMO Statement of the State of the Global Climate in 2017X
• South Asia, particularly India and China, which between 1900 and 2012 had the largest population affected by drought. ^{14 14}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013X
• The Mediterranean region experienced severe droughts in 2017, with some countries recording the driest year or season. Italy had the most severe anomalies with the driest year on record. ^{15 15}WMO Statement of the State of the Global Climate in 2017X
• Brazil has experienced multi-year droughts several times; the last one lasting for 7 years from 2011 to 2017, causing severe impacts on livestock, fisheries, agricultural production and adversely affecting the social and economic determinants of health. ^{16 16}Drought in the Semiarid Region of Brazil: Exposure, Vulnerabilities and Health Impacts from the Perspectives of Local Actors. Sena et al. 2018X
• Australia has experienced dry conditions and rainfall deficiencies ranging from 8 months to nine years, with the extreme record in the northern half of New South Wales and adjacent southern inland Queensland. Drought over eastern Australia in 2018 affected crop production, farmers’ income and the Australian economy broadly. ^{17 17}The Millennium Drought in southeast Australia (2001–2009): Natural and human causes and implications for water resources, ecosystems, economy, and society. van Dijk et al. 2013; Bureau of Meteorology. Australian Government; 2020; Climate Council of Australia Limited; 2019. Weather Gone Wild: Climate change-fuelled extreme weather in 2018X
• In the USA, drought is the second-most costly natural disaster after hurricanes, with an average of USD 9.6. billion in loss and damage per event. From 2012-2016 California recorded the worst drought in 1,200 years, seriously impacting on populations dependent on fishery and agriculture production. ^{18 18} NRDC: Drought: Everything you need to knowX

The health impacts of drought are primarily indirect – meaning they are linked to other circumstances, such as loss of livelihoods.^{19 19}2021 GAR SRD; Stanke et al., 2013; Sena et al., 2014; Yusa et al., 2015; Ebi and Bowen, 2016X

Drought-driven water and food shortages increase the risk of death and illness, especially for already vulnerable populations. Drought can cause or exacerbate health risks including malnutrition, infectious diseases, non-communicable diseases, and mental health conditions.

The primary mechanism by which drought impacts human health is by disrupting water supply to communities. This disruption can affect the availability of water for agricultural purposes, hygiene and sanitation, and lead to alternative water storage practices that can create favourable conditions for the proliferation of infectious vector-borne diseases. 

Nutrition-related health effects result from the disruption of agricultural production, which decreases the availability of food and can result in malnutrition, micronutrient deficiencies, and anti-nutrient consumption. ^{20 20}Managing the health impacts of drought in Brazil. Sena et al., 2014; Extreme events as sources of health vulnerability: Drought as an example. Ebi & Bowen 2015; Health effects of drought: a systematic review of the evidence. Stanke et al. 2013; WHO / WMO Atlas of Health and Climate, 2012X   Drought is considered the most serious climate hazard to livestock and crops in nearly every part of the world. 

Water-related health effects result from the contamination of water supplies, and from lack of access to water, sanitation and hygiene. Water can become contaminated through low water flows that cause stagnation and reduce dilution capacity, higher temperatures that encourage pathogen growth, and saltwater intrusion into coastal aquifers. Increased concentration of pollutants occur when conditions are drier, and this can be of concern for groundwater sources that are already of low quality. Lack of water quality and quantity can lead to several infectious diseases such as intestinal nematode diseases, diarrhoeal diseases, hepatitis A, eye infections (e.g. conjunctivitis, trachoma), skin infections (e.g. scabies), and also dehydration. In addition, water scarcity indirectly impacts cardiovascular and mental health. ^{21 21}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013; Managing the health impacts of drought in Brazil. Sena et al., 2014; Extreme events as sources of health vulnerability: Drought as an example. Ebi & Bowen, 2015; Drought in the Semiarid Region of Brazil: Exposure, Vulnerabilities and Health Impacts from the Perspectives of Local Actors. Sena et al. 2018X

Airborne and dust-related diseases can be exacerbated by drought when pathogens and persistent organic pollutants are transported by mineral dust. High temperatures associated with drought can lead to excessive soil and vegetation drying, increasing the mobilisation of these dusts and causing irritation to the lungs and bronchial passages. Inhalation of particles can cause direct trauma or diseases such as cardiovascular disease, and exacerbate existing conditions such as asthma. Dry seasons coupled with low humidity and air-borne dust concentrations can increase risk for meningococcal meningitis. Hazardous air dust particles also include fine mineral particulates, pollutants, spores, fungi, bacteria and potential allergens. For example, mineral dust can cause liver and kidney cancer, affect cardiovascular and respiratory health, and cause renal failure; while fungal spores can cause coccidioidomycosis (Valley fever). ^{22 22}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013; WHO Factsheet: Meningococcal Meningitis; Desert dust and human health disorders. Goudie A.S. 2014; Land under pressure – health under stress. Sena, 2019; Global Health Impacts of Dust Storms: A Systematic Review, Aghababaeian et al 2021X

Vector-borne diseases are influenced by drought when the behaviours of insect vectors, such as mosquitoes and sandflies are changed. ^{23 23}US CDC Drought Communication Toolkit: Information for Vulnerable PopulationsX  Drought conditions may also encourage residential water storage, which can increase the number of breeding sites for mosquito species that transmit malaria, dengue and other vector-borne diseases. ^{24 24}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013X

Mental Health: Drought can have a severe impact on mental health by placing affected populations under economic and financial stress. ^{25 25}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013; Climate change and mental health: A causal pathways framework.Berry et al. 2010X  Other risks for mental health conditions are linked to stress regarding family subsistence, uncertainty, and forced migration, including family separation, identity loss and social exclusion. ^{26 26}The Mental Health Outcomes of Drought: A Systematic Review and Causal Process Diagram. Vins, Bell, Saha and Hess, 2015; Drought-related stress among farmers: findings from the Australian Rural Mental Health Study. Austin et al. 2018X

Migration can lead to increased crowding among displaced populations, leading to exposure to new pathogens and spread of diseases such as meningococcal meningitis. Displaced people can also experience changes in hygiene practices, leading to other infectious diseases. Changes to family structure and dynamics can also lead to mental stress. Most migration associated with drought is from rural to urban areas and is related to poverty, food insecurity, social vulnerability, unemployment, or low income. ^{27 27}Climate change, drought and human health in Canada. Yusa, Berry, Cheng, Ogden et al. 2015; The Global Land Outlook, first edition. UNCCD 2017b; The State of Food and Agriculture 2018. Migration, agriculture and rural development. FAO, 2018X

Social and economic drivers can increase health vulnerability to drought. Race, gender, ethnicity, social inequalities, and cultural behaviours can impact health and access to resources. ^{28 28}Land under pressure – health under stress. Sena 2019X

Examples of vulnerable populations that can experience heightened impact from droughts include:

• rural communities that depend on subsistence agriculture and/or have poor irrigation or have inadequate water supply and sanitation systems;
• indigenous communities that depend on local natural resources;
• women and children that are expected to collect water from long distances or lack privacy or security in emergency shelters;
• older people show higher vulnerability to impacts associated to air pollution and to contaminated water, food and dust pollutants;
• people without free access to healthcare services or with some pre-existing health conditions, such as undernutrition, cardiovascular and respiratory diseases. ^{29 29}Drought in the Semiarid Region of Brazil: Exposure, Vulnerabilities and Health Impacts from the Perspectives of Local Actors. Sena et al. 2018X

Rising temperatures caused by climate change are making already dry regions drier, and wet regions wetter. In dry regions, this means that when temperatures rise, water evaporates more quickly, and increases the risk of drought or prolongs periods of drought. ^{30 30}WHO: DroughtX

Increasing temperatures and changes to weather patterns around the world as a result of climate change are likely to create heightened water stress, increasing the risk and exposure to drought events. Southern Europe and West Africa have observed a lengthening of droughts and an increase in intensity since the 1950s. ^{31 31}Health effects of drought: a systematic review of the evidence. Stanke et al. 2013X

Ongoing effects of climate change are likely to increase the frequency and severity of future droughts, and also have significant human health consequences. ^{32 32}Drought under global warming: A review. Dai, 2011; Reduction in carbon uptake during turn of the century drought in western North America. Schwalm et al. 2012.X  Water supplies will be put under greater stress and higher temperatures will increase water demands and evaporatoration. This will reduce both the quantity and quality of food, as well as threatening crop productivity in areas that are already food insecure. ^{33 33}Historical warnings of future food insecurity with unprecedented seasonal heat. Battisti & Naylor, 2009X  Global reductions in food security are expected to have a substantial impact on undernutrition, increasing the prevalence of stunting and wasting in children. 

Responses to droughts in most parts of the world are generally reactive in terms of crisis management, but the effects of drought can be preventable. The health impacts of drought can be managed in a number of ways, including the following:

• Early warning systems can provide timely warnings of when and where drought conditions are likely to occur, giving health authorities vulnerable time to prepare. 

• Climate Resilient Water and Sanitation 

• Vaccination of populations against communicable diseases before a drought is likely to occur.

• Improved food security through the use of food and seed banks, implementing sustainable food systems and resilient agricultural practices, ensuring political commitments to support integrative actions on local food production and reducing reliance on monocultures.

• Improved water and land management practices.

• Water conservation and management practices, especially in agriculture, can help reduce wasting of water during prolonged dry periods.