Climate change affects health
The scientific community shares an increasing sense of alarm that global warming and climate change will have a major negative impact on human health, especially in Africa.
It is thought that infectious diseases such as malaria, dengue fever and rift valley fever will spread due to global warming, raising fears that diseases that were previously thought of as only tropical or subtropical, may migrate into cooler regions. Many are concerned that global warming will expand the range of infectious diseases, because replication is enhanced by increased temperature.
Climate change and infectious disease is a complex subject involving a variety of factors. Infectious diseases can be affected by global warming, usually with a number of hosts with several life cycles, making it challenging to understand how warming would affect the spread of disease, with non-climate-related factors playing a more significant role.
While the impact of warming is hard to judge, it is clear that many diseases are directly affected by weather.
Influenza, for instance, was restricted almost entirely to winter. Scientists are still not sure why this is the case. Measles and rubella occurred mostly in late winter and early spring, while rotavirus was primarily a winter disease.
Changes in the weather have an indirect impact on the spread of disease when natural habitats are affected. For example, the deadly Hantavirus Pulmonary Syndrome, which kills nearly fifty per cent of those infected is carried by the deer mouse, the cotton rat and other rodents in North and South America. The El Nino floods and intense rainfall led to abundant growth of nuts, seeds and insects which led to a rising rodent population. It has been long known that rodents are a major contributor to the spread of many diseases.
When inhaled by humans, Hantavirus settles in the lungs and results in pulmonary disease. Spring is the most common time for infection, as this is typically when spring cleaning kicks up dust and other particles able to be carried by air. It is also the time of year when male rodents become active leaving droppings that are swept up into the air. This illustrates the indirect affect of climate change on human health.
In Malaysia in the 1990s, there was an epidemic of the Nipah virus which has a 40 per cent fatality rate. The disease was spread by pigs and the flying fox. .
The flying fox is the natural host for the virus and usually lives in dense forest areas. However, deforestation and the extreme haze caused by the ‘slash and burn’ method of clearing of forests in the area have severely impacted on flowering and fruiting forest trees. The flying fox forest habitat is being threatened by human activity. This forced them to agricultural land and from there the virus found its way into pigs. Both animals were infected and passed the Nipah virus to people. .
This example shows the complex interaction between animal hosts and humans and the weather. The epidemic was controlled only by officials having to kill almost one million pigs.
Understanding the relationship between climate change and disease was first studied by Jacob Herle a scientist over 150 years ago. Over the past century, further study and research continued to verify this link and it is now embraced by the scientific community and the public at large.
Today the greenhouse effect is clearly understood as pollution of the atmosphere continues to erode the ozone cover around the world. As we now know, greenhouse gases form a layer around the earth which prevents heat from going out of the atmosphere and, instead, bounces it back in toward earth and causes global warming. .
It is thought by the scientific community that the earth now has a higher surface temperature than at any time in the past 100,000 years. The heating up isn’t over either. It has been estimated that temperatures could raise another 2C to 5C by the end of the century. It could mean a hastening of an ice age.
The long-term effects of greenhouse gas production on infectious disease are still unknown. But some scientists think that global warming will have a devastating impact on malaria, with perhaps an additional 70-million people living in malaria areas by 2080. It is even thought by some scientists that Britain may have a malaria outbreak by the year 2050.
Cholera is another disease that affects millions around the globe. It too is on the rise as the globe heats up. Cholera is found in water and scientists have linked seasonal changes in the surface temperature and the height of the sea with outbreaks of the disease. When sea water heats up, it causes plankton to multiply. When that plankton rich water is carried into new areas it results in further outbreaks.
However, not everyone agrees that global warming is the culprit in the rise of certain diseases. The American Centre for Disease Control for instance says such claims are not scientifically proven and that the spread of malaria is the result of non-climate factors, such as failures in malaria control and the increase in poverty. The Centre promotes the vital role of people in limiting infectious diseases despite how quickly the temperature rises. The primary factors to be taken on a global scale in disease prevention are clean water, improved sanitation and reduction in poverty.
Even though it is evident that global warming and climate change will have an impact on infectious diseases, it remains difficult to judge the extent of the impact.
