Home HealthTopics Health Centers Reference Library Research
Join us on Facebook Join us on Facebook Share on Facebook

Infectious Diseases

The terms “infection” and “disease” are not synonymous. An infection results when a pathogen invades and begins growing within a host. Disease results only if and when, as a consequence of the invasion and growth of a pathogen, tissue function is impaired.

An infectious disease is a disease that is caused by a microorganism, such as a bacterium, virus, or parasite, that is not normally found in the body and is capable of causing infection. Our bodies have defense mechanisms to prevent infection and, should those mechanisms fail, to prevent disease after infection occurs. Some, but not all, infectious diseases are contagious, meaning they can spread from person to person. Other infectious diseases can spread from animals or insects to humans, but not from person to person.

Infectious diseases are responsible for more than 25% of 57 million annual deaths worldwide. 2/3 of 9 million pediatric deaths yearly are from infectious disease. Some of those deaths could be prevented with vaccines. Some infectious agents are easily transmitted (that is, they are very contagious), but they are not very likely to cause disease (that is, they are not very virulent).

(More)


Understanding Infectious Diseases

  • Infectious Diseases (OSU Patient Education)
  • Infectious Diseases (MedlinePlus)
  • Overview of Infectious Diseases (American Academy of Pediatrics)
  • Bacterial Infections (MedlinePlus)
  • Fungal Infections (MedlinePlus)
  • Infectious Disease Fact Sheets (World Health Organization)
  • Infectious Diseases from A to Z (National Institute of Allergy and Infectious Diseases)
  • Parasitic Diseases (MedlinePlus)
  • Viral Infections (MedlinePlus)
  • Understanding Quarantine and Isolation (Centers for Disease Control)

  • Commonly Asked Questions


    View All Q&As

  • Infection Control Questions
  • Q&A: Infectious diseases (World Health Organization)
  • Questions and Answers about Flu Vaccination (Flu.gov)
  • Vaccines FAQs (Centers for Disease Control and Prevention)
  • What Is a Vaccine? (National Institute of Allergy and Infectious Diseases)
  • What is an Infectious Disease?
  • What is the Immune System? (National Institute of Allergy and Infectious Diseases)

  • Additional Information

  • The Body
  • Research Studies
  • Info by Age, Ethnicity, Sex
  • Meet Our Experts

    NetWellness Expert Lisa A Haglund

    Lisa A Haglund, MD
    University of Cincinnati

    Other Experts

    Last Updated: Mar 07, 2014