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Magnified image of the novel Coronavirus ( Image Source UN Environment)

Examples of deadly zoonotic diseases

By David Okul
April 28, 2020

The emergence of Covid-19 has increased the discussion of conditions arising from animals. Zoonotic diseases, also known as a zoonosis, are diseases transmitted by germs from animals to humans. The zoonotic diseases are caused by harmful germs such as bacteria, viruses, fungi, or parasites. Once these germs/pathogens enter the human body, they cause the development of illness. A worrying trend is the observation of the increasing number of zoonotic diseases. A study by CDC estimates that three in every four emerging diseases are infectious diseases and are transmitted from the animals to humans. Scientist argues that even healthy animals can carry germs that make humans sick.

Scientists have established the link between the destruction of nature and the emergence of zoonotic diseases. As humans encroach the natural ecosystems, the chances of transmission between animals and humans increase. Similarly, wet markets provide an increased opportunity for viruses and other pathogens to jump from animals to humans.

 Some examples of deadly zoonotic diseases include Ebola, Influenza, Covid-19, and SARS.


           Ebola is an infectious disease that is caused by the Ebola virus, which is suspected of having originated from Central Africa. The Ebola virus disease was first identified in DRC in 1976. According to various studies, the Ebola virus originated from the gorillas and the chimpanzee. However, the CDC believes that the virus was transmitted through either infected bats or infected primates. It shifted from the primates to humans through human contact with infected blood fluids. The Ebola virus then spread from human to human by coming to close contact with the infected persons. 

           The common symptoms of Ebola virus diseases include muscle aches, sore throat, severe headaches, fever, vomiting, diarrhea, impaired liver, and kidney functioning, and general weakness of the body. Other severe symptoms include the internal bleeding of the gastrointestinal tract. Patients with internal bleeding cough up blood stains, vomiting blood, and there are bloodstains in their stools. This loss of blood and body fluids eventually causes deaths. However, if there is no internal bleeding, patients can recover between 7 and 14 days. According to the World Health Organization, the Ebola Virus disease has a fatality rate of 50% in some countries. In some areas, the fatality is as low as 25% or as high as 90% in stressful situations.


           Influenza is an infectious disease caused by the H1N1 influenza virus. In 1918, Influenza became a global pandemic that killed approximately 50 million people within months. Influenza originated from birds and pigs and is said to have originated from South East Asia. Influenza spreads from person to person by breathing air droplets produced by infected persons. Also, the Influenza can be transmitted by touching germs from the objects and surfaces and then touching your nose, mouth, or eyes.

The symptoms of Influenza include common cold, sore throat, sneezing, headaches, aching muscles, persistent cough, nasal congestions, and fatigue. However, some populations may increase the risk factors for developing severe complications. For instance, the elderly and people with underlying health conditions are at risk of developing complications such as pneumonia, bronchitis, and heart problems that eventually cause deaths. On the other hand, the young and healthy persons infected by the virus are likely to recover between 7 to 14 days.

           It can be prevented through annual vaccination against the flu. Other methods used to contain the spread of Influenza include washing hands, avoiding overcrowded places, and covering the mouth when sneezing or coughing.

Novel Coronavirus
Magnified image of the novel Coronavirus ( Image Source UN Environment)


           The Covid-19 is a new infectious disease caused by the coronavirus, as it was first identified in December 2019 in Wuhan, China. Many researchers believe Covid-19 originated from persons coming into contact with bats infected by the coronavirus. The respiratory disease has flu-like symptoms. The symptoms include persistent cough, difficulty in breathing, fever, and sneezing. In severe cases, the lungs collapse, causing shortness of breath leading to death. The incubation period of the virus is between 5 and 14 days. However, people showing no symptoms can transmit the coronavirus to other persons if they come into close contact.

           Covid-19 is transmitted from person to person by breathing in air droplets from infected persons. Also, the people can pick up Covid-19 by touching coronavirus germs on objects and then touching their nose, eyes, or mouth. The vulnerable populations are the older person with age above 65 years and persons with underlying conditions. The young and healthy can recover from Covid-19 between 7 and 14 days.

As of April 2020, there was no vaccine capable of protecting people from getting Covid-19. Nevertheless, the process of developing a vaccine has begun clinical trials and is expected to be ready in early 2021. As such, people are encouraged to control the spread of Covid-19 by regularly washing hands, avoiding overcrowded places, reducing contact with the elderly and people with underlying conditions, keep at least one meter distance between persons, and staying at home.


           The Severe Acute Respiratory Syndrome disease (SARS) was first identified in China in 2003. The SARS was caused by a SARS coronavirus that originated from bats and later spread to other animals such as the civet cats. The SARS then started to transmit from persons to persons through breathing in air droplets from infected persons. Also, people could pick the SARS coronavirus by touching contaminated objects and surfaces and then touching their nose, eyes, and mouth. Kissing, sharing drinks, and skin contact are other ways that SARS can be transmitted from person to person.

           The symptoms of SARS include fever, diarrhea, shivering, headaches, malaise, and pain in the muscles, cough, and shortness of the breath. The SARS symptoms were similar to Influenza, and there was no diagnostic symptom that was individually associated with SARS. For instance, some individuals showed a fever in the first weeks, shortness of breath and dry cough on the second week, and eventually patients suffering from respiratory distress.

           No vaccine has been developed to prevent SARS. However, research on a vaccine is still ongoing. People are recommended to keep a distance with SARS symptoms and avoid traveling into areas with SARS outbreak.

           Animals are beneficial to human beings for a variety of reasons. However, in recent years the emergence of Zoonotic diseases has shown that animals are also capable of carrying pathogens and transmitting them to humans. Ebola, Covid-19, Influenza, and SARS are some of the deadly zoonotic diseases that originated from animals and later transmitted from persons to persons. The five diseases in this article are just a tip of the iceberg. There are dozens of deadly zoonotic diseases as highlighted by this article.

Most of these diseases are infectious, thus posing higher health risks to humans.


Coronavirus Diseases 2019 (Covid-19). (2020). Mayo Clinic. Retrieved from

Influenza (Flu). (2019). Mayo Clinic. Retrieved from

SARS (Severe Acute Respiratory Syndrome.). World Health Organizations. Retrieved from

Zoonotic Diseases. (2017). CDC. Retrieved from

David Okul is an environmental management professional with over 10 years experience on donor projects, forestry, and community-based natural resources management.