Infectious Disease
Germs spread between people and cause illness.
About this topic
Infectious (communicable) diseases are caused by pathogens and can pass from person to person. Transmission occurs via droplets, contact, contaminated water or food, blood, vectors like mosquitoes, and from mother to baby. Spread is limited by hygiene, quarantine, vaccines, safe water, sanitation and controlling vectors.
The immune system fights infection with white blood cells. Phagocytes engulf pathogens, while lymphocytes produce antibodies specific to each antigen and memory cells that respond faster the second time. Vaccines contain weakened or dead pathogens or parts of them, so the body builds memory without suffering the disease.
When enough people are vaccinated, herd immunity protects those who cannot be, such as newborns, because the pathogen struggles to find new hosts. Smallpox was eradicated by vaccination, and polio is close to being so. Epidemics spread within a region, while pandemics spread worldwide, as with COVID-19. Measles needs about 95% vaccination to prevent outbreaks.
Treatment varies: antibiotics for bacteria, antivirals for some viruses. A common misconception is that vaccines cause the disease they prevent; they do not. Another is that antibiotics cure colds, which are viral. Good hygiene is the cheapest defence.
Key ideas
- Transmission routes
- Incubation period
- Symptoms and treatment
Quick check
Use cases: where Infectious Disease helps
- Homework: review the key idea behind Infectious Disease before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Infectious Disease without notes.
- Visual learning: play with the interactive lab to see how Infectious Disease changes when you adjust its inputs.
- Teaching a friend: explain Infectious Disease in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Infectious Disease?
Germs spread between people and cause illness.
What will I learn in Infectious Disease?
Transmission routes. Incubation period. Symptoms and treatment.
Is Infectious Disease part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Infectious Disease lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Infectious Disease?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.