Autumn 2017 — #23

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Earthquake during El Niño led to rapid spead of Zika epidemic

Health care became dysfunctional; a harbinger of natural disasters on a warmer Earth

      Nearly seven thousand persons became infected with the Zika virus soon after a large (magnitude 7.8) earthquake ravaged coastal Ecuador in 2016. A Latin American team of scientists led by Cecilia Sorensen, MD at the University of Colorado, conclude that a strong El Niño at the time combined with the devastated infrastructure and a breakdown of social structures to propel a widespread epidemic of Zika virus (citation 1). The quake and the epidemic coincided with a strong El Niño, a natural climate anomaly that brings unusually warm and humid air and heavy rainfall to the Pacific coast of South America. The “steam-bath” atmosphere greatly accelerated the spread of Zika.

      The quake killed 660 people, displaced 9,700 people, damaged 9750 buildings, and put 720,000 people in need of humanitarian assistance (2). It savaged the health care and sanitation infrastructure, and forced people to massively migrate into the cities (3).
     (continues, below left)

      El Niño and its opposite, La Niña, together are a natural climate variation that appears from time to time over the last few thousands of years. Each time the local weather/ seasonal climate are altered anywhere from a few months to two years. On the west coast of South America, El Niño brings high temperatures and humidity, and rainfall well above normal. Whether or not a climate variation is natural (an “unnatural” variation might be one caused by human influences), the different weather conditions can promote illness or make it difficult for a society to recover from a natural disaster.   (The plight of Puerto Rico after hurricane Maria breezed through in September 2017 comes to mind.)

      The quake hit Ecuador only three months after the Zika virus arrived in there in 2016, and El Niño was already in progress. Mosquitoes, specifically the species Aedes aegypti, transmit the Zika virus from person to person. This same mosquito also carries the viruses that sicken people with Dengue fever and Chikungunya fever.

      Sorensen's team asserts that the “social vulnerability” of that region made the health crisis unmanageable. The Intergovernmental Panel on Climate Change (IPCC) defines social vulnerability as the degree that a country cannot adapt to any external change by altering its practices to offset potential damages. In Ecuador, poor housing, the lack of piped water in homes, and the marginal health care system allowed the mosquito population to explode and spread the Zika virus quickly. The bar graph at the right shows how quickly the illness spread: from zero to ten cases cases before the quake, to 300 cases ten weeks later. After the quake, people slept outdoors where they felt safe but were exposed to mosquito bites. With no running water piped into their homes, people stored water in open cisterns where mosquito larvae breed.

      The short-term climate conditions that El Niño ushered in -- warmer temperatures at night, high humidity, and heavy rainfall – fostered an explosion of mosquitoes. Health officials had already blamed such conditions for the rapid spread of Dengue fever by the same species of mosquito. Because there were always more cases of Dengue fever than of Zika, the health of the population and the ability of the health care system to deal with it were already strained by the Dengue fever epidemic.

Above: The confirmed number of cases of Zika in Ecuador, for every week in 2016 and part of 2017.The yellow circle marks the week of the earthquake in April 2016. (Data from Ecuadorian Ministry of Public Health.)

      Sorenson does not attribute the spread of Zika to global climate change. The anomalous weather during El Niño is temporary and natural. However, she points out that global climate is currently taking a direction toward warmer and wetter conditions that are known to boost the spread of infectious diseases.

       Areas that are already stressed by short-term climate changes like El Niño can be sent over the edge by a natural catastrophe. The bottom line is that we would be wise to prepare in advance for a health crisis when a natural disaster strikes during anomalous climatic conditions, especially in a region “socially vulnerable” to disasters. When social structures like the police, emergency responders, and the supply of water and food broke down in Ecuador, a health crisis spiraled out of control. In our future warmer climate on Earth, extreme weather, especially extreme rainfall, are predicted to become more frequent. What would the consequences be? Serious humanitarian crises after natural disasters.

       The authors recommend practices for society to prepare for a difficult future in health care. They encompass greater cooperation between sectors of society that deal with disasters: the health care industry, the government, the research enterprise, and the emergency response folks.

News Forthcoming -- in November

  • The record hurricane season of 2017 in North America and the Atlantic: what was different this year?

  • Are grass-fed cattle really better for the climate than those on feedlots?

  • The last remnant of the Ice Age in North America is about to disappear




1. “Climate Variability,Vulnerability, and Natural Disasters: A Case Study of Zika Virus in Manabi, Ecuador Following the 2016 Earthquake” by Cecilia J. Sorensen , M J. Borbor-Cordova, E. Calvello-Hynes, A Diaz, J. Lemery, and A. Stewart-Ibarra.   GeoHealth, vol. 1. (Early View Article published online before inclusion in a journal issue) –------ available with open access at:

2. Pan American Health Organization (2016): “The Earthquake in Ecuador: Significant damage to health facilities; emergency medical teams deployed.” Disasters, World Health Organization/Pan American Health Organization, June 2016, vol. 121, 1-3.

3. United States Agency for International Development (USAID, 2016): “Ecuador - Earthquake.” Fact sheet #5, Fiscal year 2016.

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