Diagnosis
Sometimes your healthcare provider can diagnose an infectious disease by listening to your medical history and doing a physical exam. For example, listening to you describe what happened and any symptoms you have noticed plays an important part in helping your doctor find out what’s wrong.
Blood and urine tests are other ways to diagnose an infection. A laboratory expert can sometimes see the offending microbe in a sample of blood or urine viewed under a microscope. One or both of these tests may be the only way to determine what caused the infection, or they may be used to confirm a diagnosis that was made based on taking a medical history and doing a physical exam.
In another type of test, your healthcare provider will take a sample of blood or other body fluid, such as vaginal secretion, and then put it into a special container called a Petri dish to see if any microbe “grows.” This test is called a culture. Certain bacteria, such as chlamydia and strep, and viruses, such as herpes simplex, usually can be identified using this method.
X-rays, scans, and biopsies (taking a tiny sample of tissue from the infected area and inspecting it under a microscope) are among other tools the doctor can use to make an accurate diagnosis.
All of the above procedures are relatively safe, and some can be done in your doctor’s office or a clinic. Others pose a higher risk to you because they involve procedures that go inside your body. One such invasive procedure is taking a biopsy from an internal organ. For example, one way a doctor can diagnose Pneumocystis carinii pneumonia, a lung disease caused by a fungus, is by doing a biopsy on lung tissue and then examining the sample under a microscope.