Infectious diseases are disorders that are caused by germs or things like a bacteria, a virus, a fungus or a parasite.
Infectious diseases can range from mild to severe. Here are some common examples for each type:
These diseases are typically spread through various means, including direct contact, contaminated food or water, insect bites, or respiratory droplets.
Organisms live in our bodies and are typically harmless, however, certain conditions may cause the organisms to spread infectious diseases that can be spread from person to person.
Some infectious diseases can be spread by insects or animals.
These health threats are called zoonotic infectious diseases, and recent outbreaks include COVID-19 and Ebola.
“In the age of COVID-19, it is understandable that many people may not realize how many outbreaks of other infectious diseases are caused by complex, intertwined ecological and socioeconomic conditions,” lead author Patrick Stephens, an associate research professor at the University of Georgia’s Odum School of Ecology in Athens says.
His team analyzed 4,400 zoonotic disease outbreaks worldwide since 1974. They identified the 100 largest, all of which infected thousands to hundreds of thousands of people. These were compared with 200 outbreaks that included 43 or fewer cases.
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Contaminated water is the leading cause of large-scale outbreaks of infectious diseases that can be transmitted from animals to people, researchers say.
Water contamination was the most common cause of large outbreaks and the second most common cause of smaller ones. Examples of these water-associated diseases include hepatitis E, typhoid and dysentery.
Protect yourself from waterborne illnesses with the following tips from the CDC:
Large outbreaks are often driven by viral pathogens due to their high transmission potential and adaptability. Notable examples include SARS coronavirus, influenza virus, and Japanese encephalitis virus, each capable of rapid spread through respiratory droplets, vectors like mosquitoes, or direct contact.
These viral pathogens often lead to large outbreaks because of:
“We know that factors like exposure to wild mammals, habitat disruption, international trade and travel and contact with contaminated food and water are important considerations,” Stephens said in a university news release.
“Perhaps two-thirds of future infectious disease outbreaks are expected to be caused by zoonotic pathogens, and the number of these diseases is growing worldwide,” he adds. “Our research is an extremely important first step to better understand global variation in the drivers of outbreaks.”
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Smaller outbreaks are typically linked to localized factors such as food contamination, local livestock production, or direct human-animal contact. These events are often confined to specific regions and populations, arising from incidents like the spread of foodborne pathogens (e.g., Salmonella or E. coli), zoonotic diseases from livestock, or contamination during food processing.
In contrast, larger outbreaks often involve more diverse factors, such as highly transmissible pathogens, global travel, densely populated areas, or environmental changes that facilitate widespread spread. According to findings published in Philosophical Transactions B, large outbreaks are driven by a combination of viral, bacterial, or parasitic pathogens, with viral pathogens like SARS-CoV-2 and influenza playing a dominant role. Smaller outbreaks are generally more manageable but still require swift local interventions to prevent escalation.
Signs and symptoms of infectious diseases vary depending on the organism causing the infection, but often include fever and fatigue. Mild infections often respond to rest and home remedies. However, life-threatening infections may require hospitalization.
General signs and symptoms common to several infectious diseases include:
Many infectious diseases, such as measles and chickenpox, can be prevented by vaccines. Frequent and thorough hand-washing will also help protect you from most infectious diseases.
If you experience any of the following, you should consult with your doctor:
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