Infectious Disease Doctor

What is an infectious disease doctor?

An infectious disease (ID) doctor or infectious disease specialist is a physician who specializes in infectious diseases.

Infectious diseases are illnesses caused by harmful organisms that get into your body. The most common causes of infectious diseases are viruses, bacteria, fungi and parasites. These organisms are everywhere. Most of the time, we coexist with some of them without them ever causing a problem. But they can also cause diseases that range from mild to deadly.

Infectious diseases usually spread from person to person, through contaminated food, water and soil, or through insect and animal bites. Infectious diseases can affect your skin, urinary tract, lungs, blood and virtually any area of your body.

Infectious diseases are extremely common worldwide, but some are more common than others. The flu, measles, common cold, strep throat, COVID-19 and salmonella are all examples of infectious diseases.

You don’t need to see an infectious disease doctor anytime you have a virus or infection. Most healthcare providers can treat common infections and viruses. An infectious disease doctor is an expert in diagnosing, managing and treating rare, complex, serious or chronic infections. In some ways, they’re like detectives of organisms in the human body, considering tiny details of a person’s medical history or laboratory results to try to understand and control an infectious disease.

What does an infectious disease doctor do?

An infectious disease doctor is an expert in diagnosing, managing and treating acute (sudden) and chronic (present for a long time) diseases caused by bacteria, viruses, fungi, parasites and prions. They often work alongside other physicians and specialists to diagnose and treat conditions or determine the cause of a specific symptom. They spend many hours conducting research on how organisms affect different parts of your body and how these organisms can affect our society as a whole.

They also work to understand:

• New or emerging infections or infections that change over time.
• Infections that spread mainly due to international travel.
• Antibiotics, antivirals and vaccinations.

Why would you see an infectious disease doctor?

An infectious disease doctor works with many other types of physicians and specialists. Most of the time, but not always, a primary care physician (PCP) or another specialist refers you to an infectious disease doctor. It’s typically because they need additional help diagnosing and treating an infection or virus because it’s uncommon, severe, chronic or unknown. They may refer you to an ID doctor to rule out certain infections as the cause of a medical condition.

For example, a dermatologist may ask an infectious disease doctor for help with rare skin conditions and a pulmonologist may consult with an infectious disease specialist if a person has chronic or untreatable pneumonia.

Some of the ways infectious disease specialists help other healthcare providers are by:

• Diagnosing rare or complex infections or viruses.
• Identifying an organism causing a person’s symptoms.
• Interpreting laboratory tests like blood work.
• Treating an infection due to antibiotic resistance (antibiotics aren’t working).
• Pinpointing reasons for symptoms like unexplained high fevers or high white blood cell count.
• Providing long-term, specialized care for chronic infections like HIV/AIDS or hepatitis.
• Consulting on guidelines for antibiotics and vaccines or deciding what types of disinfectants or PPE (personal protective equipment) to use to minimize infections in healthcare settings.

What conditions do infectious disease doctors treat?

There are several dozen infectious diseases in the world. Some of the more common conditions that an infectious disease doctor would treat include:

• Clostridium difficile (C. diff).
• E. coli.
• Fevers.
• Hepatitis.
• HIV/AIDS.
• Leukocytosis (high white blood cell count).
• Lyme disease and other tick-borne diseases.
• Measles.
• Meningococcal disease.
• Mpox.
• Mumps.
• Rubella.
• Sexually transmitted infections (STIs).
• Streptococcal infections.
• Tuberculosis (TB).
• Whooping cough (pertussis).

What should I expect from an appointment with an infectious disease doctor?

Infectious disease doctors perform physical exams and take your full medical history. They’ll ask you lots of questions about your symptoms, medications and your environment. Environmental questions could include things like what pets you have, if you traveled out of the country or if you spend a lot of time outdoors or around chemicals.

Then, they’ll likely order some of the following tests to help diagnose a condition:

• Blood tests.
• Urine tests.
• Stool (poop) samples.
• Throat swabs.
• Tissue biopsies.
• Imaging scans like X-Ray, MRI, CT scans, etc.
• Spinal taps (lumbar puncture).

How do you become an infectious disease doctor?

Infectious disease doctors have a similar medical background as other doctors. But they spend many additional years understanding and learning about immunology and epidemiology. Immunology is the study of a person’s immune system and how organisms affect it. Epidemiology is a science that investigates factors that determine why diseases and disorders exist or don’t exist.

Infectious disease specialists have extensive knowledge of how and why viruses, parasites, bacteria and fungi affect your body.

This requires years of training. Infectious disease doctors complete the following:

• Undergraduate degree.
• Medical school (four years).
• Residency in internal medicine (three years).
• Fellowship in infectious diseases (usually two years).
• Specialization in a specific area like transplant infectious disease (optional one-year program).
• Board certification.

Where do infectious disease doctors work?

Some infectious disease doctors focus on research and may spend time working in public health, such as for the Centers for Disease Control and Prevention (CDC). Other infectious disease specialists are more clinical, which means they work in a hospital or community practice and visit patients regularly.

A note from Cleveland Clinic

Your primary care physician (PCP) may refer you to an infectious disease specialist if you have a specific infectious disease that may be challenging to diagnose or treat. Infectious disease doctors are experts in infections that happen due to bacteria, viruses, fungi or parasites. They work with your PCP and other healthcare providers to manage your condition and get you feeling well again.