The importance of lab testing after exposure to communicable diseases
Medically reviewed by Dr. Betsy Koickel, MD on December 2nd 2025.
Lab testing is critical to helping healthcare providers diagnose and treat communicable diseases. Early and accurate diagnosis helps you get the right treatment, but is also essential to slowing down or eliminating the spread of contagious diseases, helping minimize the risk of epidemics or pandemics. Without testing, many infections could go unnoticed until they have already been transmitted to others.
If you believe you have a communicable disease or are curious about testing, here’s what you need to know.
What are communicable diseases?
Communicable diseases are illnesses that can be passed from one human or animal to another. They are caused by infectious pathogens like bacteria, viruses, fungi or parasites.
These diseases are spread through different routes. For example, some require direct contact like kissing or touching, others can be passed through droplets in the air when people cough or sneeze and some through contaminated food, water or insect bites.
Examples of communicable diseases include measles, the flu, tuberculosis, HIV, malaria and COVID-19. These illnesses vary widely in severity, ranging from mild colds to life-threatening infections that require urgent care.
Why lab testing is crucial after exposure to infections
Lab testing can help healthcare providers make an accurate diagnosis. Many infectious diseases have similar symptoms and, therefore, can be challenging to tell apart based on a review of symptoms or a physical exam.
A lab test can identify the exact pathogen, which helps healthcare providers decide on the right treatment. It also helps prevent the use of unnecessary or ineffective medications.
Tests also matter for timing. Some infections have a “window period” where the body has not yet shown symptoms, but the infection is already present. Early testing can detect infection before symptoms develop, so your provider can start treatment quickly, which can help prevent complications.
Finally, lab testing is important for public health. Confirmed cases help track outbreaks, identify sources of infection and prevent further spread in schools, workplaces, and communities. By confirming cases, health officials can implement control measures like vaccination drives, isolation protocols or improved sanitation to stop or slow the spread.
Common communicable diseases that require lab testing
A few common communicable diseases that require lab tests include:
- Chlamydia
- COVID-19
- Gonorrhea
- Hepatitis B
- Hepatitis C
- HIV
- Malaria
- Syphilis
- Tuberculosis
How lab tests help detect infections early
Lab tests help detect infections early by identifying pathogens in the body before symptoms become severe, even at the earliest stages. Early testing means treatment can start sooner, which lowers the risk of complications and long-term health issues.
Early testing also reduces the chance of unknowingly spreading the infection to others. Overall, early testing is the most effective way to protect both individual health and public safety.
When to seek lab testing after exposure
You should seek lab testing for communicable diseases if you have been exposed to people who are ill, were in a high-risk setting or if you develop symptoms. Testing may also be advised when public health guidelines recommend it after specific exposures, such as to tuberculosis, HIV or COVID-19.
FAQ
Here are some frequently asked questions about communicable disease lab tests.
How do I know if I need lab testing after exposure to a communicable disease?
You may need lab testing after exposure to a communicable disease if you had close contact with an infected person, were in a high-risk setting or are showing early signs of illness. Speak to your healthcare provider if you are unsure if you need testing.
Can lab testing identify all communicable diseases, including new or emerging ones?
Lab testing can identify many communicable diseases, but not all. New or emerging infections may require specialized tests that are not widely available at first.
How long does it take to get results from lab tests for communicable diseases?
The time to get results depends on the test: rapid tests may give results in minutes or hours, while cultures or specialized tests can take several days.
Can lab testing be used for people who have already developed symptoms of a communicable disease?
Yes, lab testing is often used after symptoms appear to confirm the diagnosis and guide treatment.
Can I get tested for multiple communicable diseases at once?
Yes, healthcare providers can order multiple tests together, especially if your symptoms could be caused by different infections.
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