Climate change: resurrecting ancient diseases and creating new ones

A new Ebola related virus spread by bats has been located in China. Known as the Měnglà virus after the region in which it was discovered, it belongs to the filovirus family that includes Ebola and the Marburg viruses. A migratory animal, bats travel patterns have changed due to changing climate conditions, and with changing travel patterns comes the spread of new pathogens.

In the Middle Ages most people never travelled more than ten miles from their place of birth. For the last 1,000 years, most people have lived sedentary lives amongst familiar flora, fauna and weather patterns. And that has meant a certain predictability and acclimatisation to infectious diseases specific to those locales.

The diseases bought by European settlers to the lands of the Americas and Australia – such as typhus, influenza, smallpox, measles – proved devastating to the indigenous populations who had not had contact with such diseases or built up a store of antibodies to combat them.

Fast forward to today and humans not only travel a lot further than they did in Medieval times, they also have to contend with a rapidly changing climate and environment.

Melting permafrost, El Niño events, changing precipitation patterns, elongating and shortening seasons, the tropicalisation of arid zones, diminished air quality, water quality, and severe eco-system disruption – are combining to create a potentially serious problem in the world of infectious disease.

In 2016, 20 people died of anthrax contracted from a 75 year-old reindeer after Siberian permafrost melted. In the late 1990s the deforestation of Peruvian rainforest led to the outbreak of 120,000 cases of malaria – malaria increases significantly after El Niño events says the World Health Organization.

And through the changing habitats and intermingling of bat species, bought on by changes to natural terrain and weather patterns, viruses like Ebola, SARS, and Nipah virus pose a significant threat to humans.

Leading Australian microbiologist, Dr Petra Derrington, explains some of the reasons why new and old infectious diseases are spreading, how they’re exacerbated by climate conditions, and what the pathology profession is doing to help combat its spread.

‘Whether it’s the bubonic plague, tuberculosis, or dengue fever, these infectious diseases can be passed directly between humans, directly from animals to humans, or via vector-borne agents – such as mosquitoes – that carry the infection between humans or from animals to humans. There are also water-borne diseases.’

‘The issue with environmental change is that everything is thrown into chaos when, for example, bats that would largely inhabit the northern hemisphere now come into contact with those from the south due to climatic change and destruction of habitat.

‘It’s a concerning situation,’ says Dr Derrington.

With four health emergencies declared by the World Health Organization since 2007 (swine flu, polio, Ebola and the Zika virus) the risks are real. The Aedes mosquito, which carries Zika, dengue fever and chikungunya, is spreading further as warm and moist environments spread.

So what happens if an outbreak occurs in Australia and how do pathologists detect, track and keep ahead of the wave?

Diagnostic testing in the context of an outbreak is important not only in determining who has the infection and ensuring they get the appropriate treatment, but also to rule out infection in patients who present with similar symptoms, so that resources can be deployed appropriately.

‘In the case of the 2009 swine flu pandemic, we were fortunate that routine tests were able to detect the infection, while we also had a large amount of global influenza data that allowed for the rapid development of a test to detect that particular strain,’ says Dr Derrington.

‘Contrast that with the Lassa Fever outbreak in Nigeria earlier this year. While we have a test available should a traveller return with a suspected case, the lack of research data means we can’t be sure that we can detect every strain of infection.

‘These kinds of situations highlight the importance of global collaboration for disease preparedness. It’s also important to note that we would not be able to manage outbreaks effectively without the assistance of our public health colleagues, who track the movements of these diseases through the community and help us find cases.’

Outbreaks of infection can be frightening, but there are ways for everyone to be prepared.

Dr Derrington recommends keeping up to date with travel recommendations through resources like smarttraveller.gov.au, and being sure to visit a travel medicine specialist before travelling overseas.

‘These doctors and nurses are specially trained to ensure you have up to date vaccinations and other appropriate preventative measures to keep you happy and healthy while travelling.’