How climate changes affect the spread of tropical diseases?
Humans have known that climatic circumstances affect epidemic diseases from long before the role of contagious agents was discovered, late in the nineteenth century. Roman aristocrats retreated to hill resorts each summer to avoid malaria. South Asians learnt early that, in high summer, strongly curried foods were less likely to cause diarrhoea.
Infectious Disease could become further familiar in a Warmer World; particularly for Plants and Animals. Climate change will make it easier for many infectious diseases to spread.
Climate change remains a ample threat to future human health and since the behavior of disease carriers like mosquitoes is known to be enormously sensitive to temperature and rainfall, it seems indisputable that climate change will affect many, if not all, of these diseases. What is less clear, however, is the extent to which climate increases the risk of becoming infected in assured regions compared to other factors such as poverty or weak health systems.
Observed and predicted climate/infectious disease links
There are three categories of research into the linkages between climatic conditions and infectious disease transmission. The first examines evidence from the recent past of associations between climate variability and infectious disease incidence. The second looks at early indicators of already-emerging infectious disease impacts of long-term climate change. The third uses the above evidence to create predictive models to approximation the future burden of infectious disease under projected climate change scenarios.
Historical Evidence
There is a lot evidence of links between climatic conditions and infectious diseases. Malaria is of immense public health anxiety, and seems likely to be the vector-borne disease most sensitive to long-term climate change. Malaria varies seasonally in highly endemic areas. The link between malaria and intense climatic events has long been studied in India, for example. Early last century, the river-irrigated Punjab region experienced periodic malaria epidemics. Excessive monsoon rainfall and high humidity was identified early on as a key influence, enhancing mosquito breeding and survival.
It’s been known for a while that warming temperatures could help certain diseases. Malaria, which kills about 650,000 people a year, thrives in the hot and humid areas where the Anopheles mosquito can live. As the climate warms, the territory where the mosquito and the malaria parasite will be able to live will likely expand, putting more people at risk. Already dengue fever, another mosquito-borne tropical disease, has re-established itself in the Florida Keys, where it was wiped out decades ago. Tropical diseases will loom that much larger in a warmer world, as host-parasite cycles accelerate. In the Arctic, which is warming faster than any other region on the planet, higher temperatures are allowing parasites like the lungworm, which afflicts musk oxen, to develop faster and be transmitted over longer periods.
World Health Organization (WHO) warns of climate impact on tropical disease spread
The World Health Organization says billions of dollars are required over the next two decades to slow the increase of diseases such as leishmaniases, dengue and chagas.
Officials say US$2.1 billion is necessary every year from 2015-2030 to prevent and control 17 deserted tropical diseases, which previously affect around one billion people in 149 countries. The extra investment would represent 0.1% of healthcare costs in affected countries over the next 15 years, says the study.
Heavy rainfall is linked to increases in dengue fever, which causes flu-like symptoms but can be fatal. Every year an estimated 390 million are infected.
The WHO says dengue has already re-emerged in countries where it has been absent for decades, along with related mosquito-borne viruses such as chikungunya and zika. It says early detection and targeting of these diseases will save money in the long run, citing success in halting the spread of guinea-worm disease through widespread treatment programmes.
Changes in risk
Infectious disease
One of the most worrying aspects of global warming is its likely impact on infectious diseases, in particular dengue fever, which risks infecting 128 countries and 3.9 billion people, more than half the world’s population. Although death rates are only around 2.5%, the disease affects so many people it represents a vast burden on the health services of affected countries. Spread by a mosquito that prefers warmer, more humid weather, and which has adapted to urban environments, dengue is now a major global health threat.
Pollution
When compared with viruses such as HIV and diseases such as malaria, air pollution – both inside and outside the home – is a far greater killer of men and women. Much of this is the result of the inefficient combustion of solid fuels on inefficient stoves in poorly ventilated homes and the widespread use of cars. By promoting clean energy, these problems would be reduced while also helping to cut carbon emissions that are the cause of global warming.
Malnutrition
Some of the world’s most significant food-producing regions are near rivers or estuaries, including the Nile, the Ganges and the Mekong basin. Rising sea levels, which climate experts fear could reach half a metre to a metre by the end of the century, threaten these zones, in particular the Mekong in Vietnam, a nation that is one of the world’s main exporters of rice.
Some Deadly Diseases Emerging from Global Warming
Reviving pathogens
As the globe warms, scientists warn about melting ice caps, rising sea levels and odd, extreme weather. But there’s another threat that may already be emerging: New (and old) diseases spreading in places once thought safe.
Anthrax, revived
In late July 2016, an outbreak of anthrax ripped through reindeer herds in Siberia, killing more than 2,000.
Zika shifts
Zika, a virus that typically causes no symptoms or mild fever and rash in adults, can be devastating when it infects pregnant women, causing miscarriage and microcephaly in fetuses.
Zombie diseases
But anthrax isn’t the only pathogen potentially biding its time in the permafrost. In 2015, researchers announced that a giant virus they’d discovered in the Siberian permafrost was still infectious — after 30,000 years.
Cholera on the rise
The deadly diarrheal disease cholera spreads through contaminated water. In a warming future, research suggests, cholera outbreaks could increase.
