The more plastic there is lying around, the greater the number of breeding places. More breeding places mean more mosquitoes and therefore, a greater chance of transmitting diseases such as malaria, Zika or dengue fever. There is a direct link between plastic debris and the risk of infectious disease. This is a major problem especially in slums in tropical areas. Floating plastic can also be a source for the spread of pathogens, including cholera bacteria. Investigations into the relationships between plastic and pathogens are just beginning and we have only recently become aware of the plastisphere.
Zika virus
In May 2015 outbreaks of Zika fever were detected in Brazil. The symptoms of Zika virus disease include fever, rash, conjunctivitis, and muscle pain. The same mosquito species also transmit dengue and chikungunya fever. In Brazil, babies with microcephaly (an abnormally small head) were born. This rare condition is caused by abnormal brain development in the womb. The World Health Organization called the Zika outbreak “a global public health emergency” and recommended preventing the accumulation of garbage – such as plastic and car tires – in open areas and covering water reservoirs to keep mosquitoes out.
Plastisphere
The plastisphere is the layer of microbial life that forms around every piece of floating plastic. These are bacterial colonies that consist of more than a thousand different organisms. German research from 2016 showed that various bacterial species of the genus Vibrio can attach themselves to floating microplastics. Vibrio bacteria are known as pathogens that can cause infections in both humans and animals. Vibrio cholerae causes cholera in humans. Plastic waste and microplastics are not, or are barely, biodegradable and so they can remain in the environment for a long time acting as vectors (a means of transport) for pathogens. In this way, plastic can spread microorganisms, including pathogens, in the sea but also in the air. Almost all microplastics examined showed weathering and the formation of a ‘plastisphere’.
