The Growing Threat Of Zoonotic Diseases: The Human-Animal Connection

Written by Nayena Sen

Edited by Abby Arora and Alice Deng

What if a single animal could trigger a global health crisis? Believe it or not, that’s exactly what has happened before—and it’s happening again. The global rise in zoonotic diseases—illnesses that pass from animals to humans—has become an urgent public health concern. Zoonotic diseases can cause significant health issues and also impact communities, economies, and ecosystems. As interactions among animals, humans, and the environment continue to increase, the threat of zoonotic diseases grows. It is therefore essential to understand and address this evolving issue from a One Health perspective.

What are Zoonotic Diseases?

Zoonotic diseases [Zoonoses], are infections that spread between animals and humans and can be caused by bacteria, viruses, parasites, or fungi. These diseases spread through consuming contaminated water and meat but also through animal bites and infected bodily fluids (Cleveland Clinic, 2024). With the rise in global travel and expanding human-wildlife interactions, how long will it be before we face another major outbreak? The risk of zoonotic diseases has risen over the years as urbanization and deforestation have become more popular. Some zoonotic diseases that are easy to recognize are:

1. COVID-19

   1. Pandemic that most likely originated from a wildlife source (World Health Organization, 2020).

2. Rabies

   1. A preventable viral disease that’s transmitted through infected animal bites (World Health Organization, 2024)

3. Ebola

   1. Disease spread through the close contact of infected animals like primates and fruit bats (Centers for Disease Control and Prevention, 2024)

4. Zika Virus

   1. It is transmitted mainly through mosquito bites but can also be connected to animal reservoirs (World Health Organization, 2022). 

The increasing risks of these diseases highlight the need and the urgency for an integrated approach to managing as well as preventing outbreaks.

How do Zoonotic Diseases spread?

There are 5 primary ways for zoonotic diseases to spread (Centers for Disease Control and Prevention, 2024):

1. Direct Contact

   1. Contact with saliva, urine, blood, mucus and feces or other bodily fluids of an infected animal.

      1. Ex. Touching/petting or bites/scratches from infected animals

2. Indirect Contact

   1. Contact with areas where the infected animal lives or objects/surfaces that have been contaminated. 

      1. Ex. Chicken coops, plants, soil, pet habitats

3. Vector-borne

   1. Bitten by a mosquito, tick or flea

4. Food-borne

   1. Eating/drinking contaminated food or water.

      1. Ex. Unpasteurized milk, undercooked meat/eggs, raw fruit/veggies that have been contaminated

5. Waterborne

   1. Drinking or being in contact with contaminated water from the feces of an infected animal.

Can you be at higher risk of serious illnesses from Zoonotic Diseases?

Yes, you can be at higher risk of serious illnesses from zoonotic diseases. Everybody, even healthy people are at risk. However, some groups are more at risk than others. These higher-risk groups are more likely to get sicker and even die from infection. These high-risk groups are labelled as children younger than 5, pregnant women, individuals older than 65 and those with weakened immune systems (Centers for Disease Control and Prevention, 2024).

Factors that are driving the increase in Zoonotic Diseases

1. Climate Change

   1. Rising temperatures affect the habitats of disease vectors such as mosquitos and ticks which allows them to thrive in new areas thereby spreading infection (Canada, 2020).

2. Deforestation & Habitat Loss

   1. Due to forests being cleared for urban development and agriculture, wildlife habitats are being affected and humans are encroaching onto those spaces. This increases the chances of human-animal contact (World Wildlife Fund). 

3. Agricultural Practices

   1. Many farming systems function where animals are densely packed which creates opportunities for pathogens to multiply and spread to humans (Hayek, M. N, 2022).

4. Global Trade & Travel

Increased movement of people and goods between countries heightens the spread of zoonotic diseases across borders (Findlater, A., & Bogoch, I. I, 2018).

The growing threat of Zoonotic Diseases

The threat of zoonotic diseases has risen in recent years, with several outbreaks demonstrating their potential to cause widespread health crises. For instance, the spread of COVID-19 showcased the vulnerability of interconnected global health systems and the need for rapid response capabilities (Filip et al., 2022). But how much longer can we ignore the clear signs that our increasing interaction with animals and the environment is fueling these outbreaks? In addition, natural ecosystems are heavily affected as increased human activities disrupt them thereby leading to the rise of zoonotic diseases which in turn pose significant challenges for public health.

How the One Health Approach Combats Zoonotic Diseases

The One Health approach is important in addressing the growing threat of zoonotic diseases. By recognizing the interconnectedness of human, animal and environmental health, One Health fosters collaboration among medical professionals, environmental scientists, policymakers and veterinarians. There are several cases where this approach has helped successfully mitigate these infections. An example is the rabies outbreak in Bhutan, Sri Lanka and Bangladesh where the infections were uncontrollable. Health officials and veterinarians worked side-by-side to implement an integrated response. Veterinarians played a key role in vaccinating dogs—major carriers of the disease—while doctors focused on treating humans who had been exposed. By combining efforts, they established a multi-faceted strategy that included surveillance, outbreak investigations, mass vaccination campaigns for both humans and dogs, laboratory testing, and effective dog population management. Due to these measures, confirmed cases dropped significantly and human fatalities decreased drastically (Horefti, E, 2023). This is just one example of many where the One Health approach has targeted and successfully helped alleviate fatalities/those affected by out-of-control diseases. Overall some key interventions include: 

1. Enhanced Surveillance

2. Improved Sanitation

3. Sustainable Practices

4. Public Health Education

Key lessons from the recent outbreak of COVID-19

The COVID-19 pandemic has shown how impactful zoonotic diseases can be on populations as well as economies worldwide. What if the next outbreak is even more devastating? It proves the need for further global collaboration to prevent, detect and respond to future outbreaks. Investing in research and stronger healthcare infrastructure is essential to help mitigate the impacts. 

Conclusion

Zoonotic diseases represent an emerging threat to global health with it being attributed to increased human-animal interactions, pathogens spreading across borders as well as environmental degradation. The One Health approach provides a comprehensive strategy to address the challenges of such diseases due to their interconnectedness. But how many more lives and economies must suffer before we take meaningful action? It is extremely important to prioritize proactive measures to help solve the impact of zoonotic diseases to have a healthy future. The next pandemic isn’t a question of if—it’s a question of when. But through collaboration, awareness, and proactive solutions, we can build a healthier, safer future for all species on this planet. The time to act is now ✨🌍✨