What to Know About Pathogens

Medically Reviewed by Murtaza Cassoobhoy, MD on May 28, 2023
4 min read

A pathogen is a living thing that causes disease. Viruses and bacteria can be pathogens, but there are also other types of pathogens. Every single living thing, even bacteria themselves, can get infected with a pathogen.

The world is full of pathogens. Experts estimate that there are more viruses on our planet than there are stars in the entire universe. Only a small portion of these microorganisms negatively affect your health. Some of them are even helpful.

Viruses and bacteria are not the only organisms that can cause disease. There are also:

Two main types of pathogens can infect you:

  1. Facultative pathogens. This type of pathogen can reproduce in a host or somewhere else, like on a surface in your home.
  2. Obligate pathogens. These microorganisms can only reproduce in a host. All viruses fall into this category since they can not reproduce on their own like bacteria or fungi. 

Additionally, some pathogens require multiple hosts. For example, deer ticks get infected with Lyme disease, which they can then pass on to you.

Some pathogens can only survive in one type of host. Other pathogens can infect a wide range of organisms. For example, tigers and primates in zoos have caught the COVID-19 virus after coming into contact with their human caregivers. Avian flu and swine flu are two other viruses that have both animals and humans as hosts. Pathogens that can spread from animals to humans are called zoonotic diseases.

There are several ways that pathogens can make you sick. Sometimes they produce toxins that damage tissue. Other times, the pathogen creates a strong immune response that damages healthy tissue along with infected tissue.

Pathogens also use this immune response to spread. Sneezing, coughing, and diarrhea are just a few ways pathogens find a new host to infect.

Pathogens spread through common human behaviors. You may cough or sneeze into your hands and then touch other things or people. You can also transfer pathogens to food by having dirty hands while cooking. Pathogens from raw food can spread to other foods in the kitchen. You can also get infected with a pathogen while changing your child's diaper or after petting an animal.

One way to avoid pathogens is to wash your hands frequently. You should especially wash your hands before preparing food, after using the bathroom or changing a diaper, and after petting any animals.

If no soap and water are available, you can use a hand sanitizer that is made of at least 60% alcohol. Hand sanitizers with less than that don't sufficiently kill pathogens.

Some pathogens are related to certain activities, with a higher rate of infections occurring in rural areas. If you're cleaning or sweeping a house, barn, or garage that's been empty for some time, for example, and you know mice have been nesting there, you can catch hantavirus simply by coming into contact with dust that's contaminated with feces and urine from rodents.

You can also become infected after entering abandoned buildings like barns or cabins that haven't been aired out. Experts recommend airing out any cabins that have not had recent inhabitants for at least 30 minutes before you enter.

Other pathogen infections occur from drinking untreated water. When camping, always sanitize water properly to avoid pathogens like giardiasis and cryptosporidium, which can both cause severe diarrhea. 

Some microorganisms are harmless and even helpful. A microorganism is only considered a pathogen if it causes disease. Harmless viruses, bacteria, fungi, protozoa, and parasites are simply called microorganisms.

Fungi. Fungi are important in nature. They help to break down dead organisms to make the nutrients accessible for new growth. The mushrooms that you eat are fungus, while bread is made with a fungus — yeast.  One extremely helpful fungus — Penicillium notatum — helps us to make the antibiotic penicillin. 

Protozoa. Some types of protozoa are useful to treat water or keep soil healthy.

Bacteria. Your gut contains helpful bacteria that keep you healthy and help you digest food. Having a healthy gut biome has even been linked to mental health and heart health. A balanced gut biome has also been linked to increased immune response, cancer prevention, and lower incidence of rheumatoid arthritis in early studies.

Viruses. Even viruses can be useful. Scientists now use viruses in gene therapy to treat certain conditions. They alter a virus so it is no longer harmful, and add whatever helpful DNA information will treat the condition. They then use the virus's natural ability to infect your cells and replicate to carry the helpful DNA into your body. This new DNA causes your cells to make a new protein, potentially helping a genetic condition. This treatment is still experimental but has been used in trials to treat cancer, heart disease, and more.