The alarming increase in animals-to-human diseases, such as Covid-19, monkeypox, MERS, Ebola, avian flu, Zika, and HIV. In recent years, these diseases have raised concerns about the possibility of new pandemics. The severity of these diseases varies, but they pose a significant threat to human health and can have devastating impacts on global economies.
Understanding zoonoses: diseases transmitted from animals to humans
Zoonoses are diseases or infections that are transmitted between animals and humans, and vice versa. These diseases can be caused by bacteria, viruses, or parasites, and they can be transmitted directly through contact between an animal and a human, or indirectly through food or vectors such as insects, spiders, or mites. According to the World Organisation for Animal Health, 60 percent of human infectious diseases are zoonotic.
Types of zoonotic diseases
Zoonotic diseases encompass a wide variety of illnesses that can affect different systems in the human body. Some examples include salmonellosis, which affects the digestive system, avian and swine flu as well as Covid-19, which affect the respiratory system, and rabies, which affects the nervous system. The severity of these diseases in humans can vary greatly depending on the disease and the virulence of the pathogen, as well as the individual’s sensitivity to the pathogen.
Animals involved in zoonotic diseases
Various animals can serve as hosts or reservoirs for zoonotic diseases. Bats, for example, have been identified as reservoirs for many viruses that can affect humans, including rabies, Ebola, SARS coronavirus, SARS-CoV-2 (which causes Covid-19), and the Nipah virus. Other animals such as badgers, ferrets, mink, weasels, cattle, pigs, dogs, foxes, camels, rodents, and ticks can also play roles as intermediate hosts or vectors in the transmission of zoonotic diseases.
Factors contributing to the increase in zoonotic diseases
There are several factors that have contributed to the increase in zoonotic diseases in recent years. One significant factor is the growth of international travel, which has facilitated the spread of diseases across borders at a faster rate. As humans continue to expand their presence and activities in different parts of the world, they disrupt ecosystems and promote the transmission of viruses. Industrial farming practices, such as intensive animal farming, can also increase the risk of pathogens spreading between animals, leading to the emergence of zoonotic diseases.
The trade in wild animals for various purposes, including food, pets, and traditional medicine, can also increase human exposure to the microbes that these animals may carry. Deforestation and habitat destruction further increase the risk of contact between wildlife, domestic animals, and human populations, providing more opportunities for the transmission of zoonotic diseases.
Impending threat of another pandemic
The consequences of the rise in animal-to-human diseases are concerning, and there is a looming threat of another pandemic. Climate change is predicted to force many animals to migrate from their natural habitats to more habitable areas, increasing the chances of mixing and transmission of viruses between species. A study published in the scientific journal Nature in 2022 warned that climate change could push animals to flee their ecosystems, leading to more transmission of viruses and potentially the emergence of new diseases that could be transmitted to humans.
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Furthermore, estimates published in the journal Science suggest that there are millions of unknown viruses in mammals and birds, with hundreds of thousands of them having the capacity to infect humans. The expansion of human activities, including encroachment into wildlife habitats and increased interactions with wildlife, also raises the risk of viruses capable of infecting humans “finding” their host and causing outbreaks of zoonotic diseases.
