What Health Risks Does Climate Change Pose?

Patient Presentation
A 9-month-old male came to clinic for his health supervision visit. His parents were graduate students at the local university and would be returning to live in China in 2 weeks. They were wondering about vaccines particularly for Japanese encephalitis because they would be living in a high risk area in China. The past medical history was unremarkable. The pertinent physical exam showed normal vital signs with growth parameters between 10-25% for height and weight and 50% for head circumference. The examination was otherwise unremarkable.

The diagnosis of a healthy male was made. The pediatrician discussed the options of starting the Japanese encephalitis vaccine in the U.S. and finishing it in China or waiting until they went to China to do the complete series there. “Japanese Encephalitis virus is more common during the warmer months, but I don’t know with the extent of climate change, if the risky time period has been extended,” the pediatrician said. Reviewing some governmental information with the parents on the computer in the room, the pediatrician was able to find out that there had been extension of the risk areas and time periods in East Asia. As it was April and the risk would be increasing, and after more discussion, the family decided to do the first Japanese Encephalitis vaccine in the U.S. and then followup with the second one once they were in China. The family felt good as this was similar to the routine Chinese vaccine schedule for infants also.

Japanese encephalitis virus (JEV) is a Flavivirae, arbovirus that is endemic to many areas of Asia and the Pacific. It is estimated to affect ~70,000 people/year with ~10-15,000 deaths yearly in 20 countries, with a fatality rate of 35-40%. It can cause encephalitis and irreversible neurological morbidity. JEV is spread by Culex mosquitos which feed on swine. Increased environmental temperature and increased humidity (warm air is more moist) increases mosquito numbers, their survivability and ultimate dissemination. China has the highest rates of JEV with particular areas being more prone, as some areas co-farm rice and swine and the families live closely to the rice paddies and livestock which encourages transmission. JEV’s range has expanded over the past few decades including in 2009 into Tibet which was thought to be immune because of its altitude. Similar geographic spread has been found in other countries too such as Australia. Mass immunization in China and other countries has decreased the disease but it still remains a threat.

Learning Point
Weather is a moment-to-moment, day-to-day event and differs from climate which occurs across seasons, many years, and regions. “Climatic conditions and weather patterns have many consequences for human physiology, health and survival. Some health impacts, as from extreme exposures such as heat waves, occur directly. However, most climate-related health risks are mediated via the influences of climatic changes and shorter term weather fluctuations on food yields, water flows, patterns of infectious disease and the movement or displacement of groups and populations. When climatic conditions change over time, then we should expect changes in patterns of health risks and in population health profiles.” Most climatic health issues are not due to direct affects, but are due to indirect effects on the environment, ecology and social impacts.

Climate change health conditions include:

  • Primary/direct health effects
    • Are from extreme events such as heat waves, floods, fires, hurricanes/typhoons, landslides, tornados, and storms. The intensity and frequency of these events obviously can affect more people more frequently.
    • Direct health impact includes injuries, hospitalizations, poisoning, death, and numerous mental health issues. Children are especially affected by mental health issues.
  • Secondary health effects
    • Air quality related problems such as allergies and asthma
      • Air pollutants (including ground level ozone changes) and aeroallergens can increase because of wildfires, rising temperatures, rainfall patterns and altered crop yields.
    • Food related problems which can affect food supply, quality and overall nutrition
      • Rainfall patterns and soil temperature affects crop and animal food yields
      • Increased contamination of food/water with bacteria or environmental pollutants (including sewage) making food/water unusable
    • Infectious disease patterns
      • Expansion of number, range and activity of host species or vector species increases the infectious disease risks
      • Examples include non-human hosts of rodents, bats and vector-born illnesses such as Dengue, Hantavirus, Japanese Encephalitis Virus, Leishmaniasis, Lyme disease, malaria, schistosomiasis, and others.
  • Tertiary health effects
    • Water changes including stocks and flows of reservoir water such as groundwater recharging and glaciers/snowpack
    • Sea water elevation can cause local changes in water quality (increased bacterial or environmental toxins) with decreased fishing, arable or grazing land.
  • Changes in food and water supplies and land availability can lead to increased epidemics, population stress, conflict, population displacement and deteriorating social structure
    • “Displacement typically entails increased risks to health from undernutrition, infectious diseases, conflict situations, mental health problems – and from changes in health related behaviors such as alcohol consumption, tobacco smoking and transactional sex.”

On the potential positive side, some climatic changes can benefit some regions such as cold-weather areas will have fewer strokes or myocardial infarctions due to winter weather. Temperate areas that become even warmer could have drier conditions and therefore fewer mosquito-borne infectious diseases as there is less water for breeding and decreased lifespan.

Questions for Further Discussion
1. What climate change health conditions have you seen locally?
2. What climate change health conditions could you expect in your local area?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Climate Change, Environmental Health, and International Health.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Kurane I. The effect of global warming on infectious diseases. Osong Public Health Res Perspect. 2010 Dec;1(1):4-9.

McMichael AJ, Lindgren E. Climate change: present and future risks to health, and necessary responses. J Intern Med. 2011 Nov;270(5):401-13.

Bai L, Morton LC, Liu Q. Climate change and mosquito-borne diseases in China: a review. Global Health. 2013 Mar 9;9:10.

Tian HY, Bi P, Cazelles B, Zhou S, et.al.. How environmental conditions impact mosquito ecology and Japanese encephalitis: an eco-epidemiological approach. Environ Int. 2015 Jun;79:17-24.

Ahdoot S, Pacheco SE; Council on Environmental Health. Global Climate Change and Children’s Health. Pediatrics. 2015 Nov;136(5):e1468-84.

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital