Heat waves mostly kill people already at risk, such as those with acute and chronic illnesses who take medication, but also people who engage in outdoor activities (sports or work), and even children and elderly people who spend time in vehicles or outdoors during the hottest parts of the day.

According to the World Health Organization and the World Meteorological Organization, a heat wave is defined as an unusually hot period lasting at least three days that impacts human beings and natural systems.

Although not a disaster that causes damages on the scale of a major earthquake or hurricane, a heat wave affects health, agriculture, and livestock, and tends to occur at the same time as electric power outages, forest fires, and drought, which have consequences for food production and livelihoods, creating disruptions in a society’s operation. According to the United States Centers for Disease Control and Prevention, heat waves cause more deaths than other natural disasters.

After the mega-heat wave that hit 16 European countries in 2003, causing an estimated 70,000 deaths, there has been an increase in the magnitude, duration, and intensity of heat waves at the global level. This has also led to a sharp increase in the demand for ambulances and emergency services, as was seen in Japan in July 2019, where a heat wave caused 57 deaths and 18,000 hospital visits in a one-week period.

In 2019, alerts have been issued in Argentina, Bahamas, Bolivia, Brazil, Canada, and the Dominican Republic, among other countries in the Region of the Americas, and heat waves are predicted for the summer of 2019-2020 in the southern hemisphere that may increase heat stress on the population, potentially causing health problems.

The heat waves with the greatest impact in the Americas were in Brazil in 2010, with a death toll of 737 over 10 days, and in Argentina, where 1,877 people died in three heat waves between December 2013 and February 2014. These events lasted an average of 6.1 days and led to massive power outages.

Heat can cause severe symptoms such as heat exhaustion and heat stroke (a condition in which inability to control high body temperature causes hot, dry skin and loss of consciousness). Most deaths are due to a worsening of cardiopulmonary, kidney, endocrine, and psychiatric diseases. Mild symptoms include swelling in the legs, rashes on the neck, cramps, headache, irritability, lethargy, and weakness.

Response to heat depends on an individual’s adaptability. Serious consequences appear suddenly, so it is very important to be attentive to alerts and recommendations from local authorities.

However, the health sector has limited capacity to respond to extreme heat waves affecting the Region. Health workers are not familiar with this risk, nor are they trained to prevent and manage illnesses caused by heat. Health facilities lack drugs, supplies, medical supplies, and equipment. Their protocols do not include heat-related illness as a differential diagnosis, and there is little public awareness of this risk, which leads to failure to take self-care measures such as staying in cool places and avoiding the sun.

Given this threat, the Pan American Health Organization prepared a guide to help the countries of the Americas develop contingency plans for heat waves. The guide provides recommendations that health-sector and meteorological agencies can follow to ensure better preparedness and response to this hazard, thereby promoting health, preventing adverse effects on people, and saving lives.

The guide and communication materials are available at: