Spread of Infectious Diseases Could be Linked to Changing Climate

Could a changing climate and changing environments have an impact on the spread of infectious diseases? At least one zoologist thinks so.

In an article posted on R&D;, one of Continuity Insights’ sister publications, zoologist Daniel Brooks of the Harold W. Manter Laboratory of Parasitology at the Univ. of Nebraska-Lincoln discussed how the spread of infectious diseases like the West Nile Virus and Ebola could be linked to changing climate.

Changes to an environment could cause animals to migrate to places they otherwise wouldn’t have gone before. If those animals carry diseases, they could introduce them to a new population.

“Disruption of wildlife ecosystems and environments can bring humans and animals closer together where the potential for animal pathogens to enter human populations can increase,” Dr. Kamran Khan, a scientist at the Keenan Research Center, said in an exclusive interview. “One example relates to Nipah virus infections in humans in Malaysia.”

Khan, associate professor of infectious diseases at the University of Toronto, cited SARS, MERS, Nipah and Ebola as diseases that caused significant consequences after being transferred from humans to animals. He also said vector borne diseases, those transmitted by insects, are on the rise.

“Vector borne diseases are reemerging today because of global changes in climatic conditions,” Khan said. “Examples include Dengue Fever, which is gradually expanding in new areas of the world, and Chikungunya, which was recently introduced into the Caribbean and is now spreading locally in parts of South America, Central America and even North America.”

While some diseases can’t be transmitted from animals to humans immediately, that can change over time.

“Given enough exposure and time, any disease can eventually mutate into a human to human transmittable disease. History is full of such occurrences,” Dan Hahn, emergency manager of Santa Rosa County, Fla., said. “The Black Death of 13th century Europe was caused by rats transmitting bubonic plague, but historical data suggests deaths occurred too rapidly for this to have been a bubonic epidemic, so recent archaeological evidence through DNA sampling of corpses buried around London has confirmed that it was pneumonic plague, a much faster acting killer, that wiped out large parts of the London population. Ebola, likewise, has had its origins traced to animals in Africa.”

Poor Healthcare

According to Khan, while changing environments can lead to an increase in the spread of infectious diseases, they are not the only factor. Dense population and poor healthcare can cause the transmission of any disease to explode.

“There are many factors here–population density and urbanization can play a role in local disease spread. In particular, weakened healthcare systems play a central role as we can see with Ebola in West Africa,” Khan said. “Changes in sanitation infrastructure are also central. From a global perspective, areas of the world that are increasingly connected through commercial air travel can lead to the transportation of diseases across vast distances.”

How to prepare

Fighting the spread of infectious diseases can be difficult, but some precautions can be taken so individuals can better prepare themselves.

“I think proper hygiene and up-to-date immunizations will protect us from a lot of diseases,” Hahn said. “Also awareness of threats. Knowing what is prevalent in areas you may travel, and how to protect yourself is critical.”

However, Khan cautions that infectious diseases are difficult to prepare for on a large scale and a lot of work must be done to stop their spread.

“These pathogens can have important health, security and economic consequences,” Khan noted. “There is no easy way to prepare for these other than having strong infectious disease surveillance systems to be able to recognize that a disease is present and robust medical and public health infrastructure to be able to respond to epidemics effectively and efficiently. From a global perspective, preparation requires strengthening the weakest links in the world where diseases can run rampant.”