Influenza, commonly called the flu, is a disease that can spread from person to person relatively easily and can infect large numbers of people. Although most people recover quickly from the flu, some people, such as the elderly, are at risk of serious illness and even death. The flu virus comes in many different forms, some of which are more dangerous than others. An influenza sample, which is a method of sampling from a person, is a way for medical professionals to check if a patient has the flu and, if so, what type of flu it is.
When the flu virus infects a person, it does so through the respiratory tract. The nose and throat are places where viral particles live and grow, and produce symptoms such as a runny nose, sore throat, and cough. These locations are also the most accessible areas for a doctor to take samples, and therefore an influenza sample most often comes from these parts of the body.
Influenza often moves rapidly through populations, and for public health reasons, some government health care agencies may want to track the movement of the disease. As the flu virus also mutates rapidly, producing new versions of the flu regularly, the type of flu a person has can also be important information for the public health system. Finally, a doctor may need to establish whether or not a person has the flu in order to follow an appropriate course of treatment.
Swabs are tools that a medical professional uses to sample an area, usually to test for the presence of germs. They often have long handles with a soft swab on the end, made of material or even plastic, and are sterile, so the test only tests for microbes present in the sampling area. During an influenza swab procedure, the physician typically inserts the end of the swab into the patient's nose and rotates the influenza swab so that it collects as much mucus as possible. The doctor may insert the swab through the nose to the top of the throat to sample that area, if it appears to have more viral growth than inside the nose.
Doctors have several different ways to test swabs for the presence of the influenza virus. The test that takes days to a week to complete is viral culture, where viral particles are grown in the laboratory on human cells. The most rapid tests include testing the sample for the presence of influenza genetic material or antigen tests. Antigens are molecules that are part of the virus that are specific to that virus, and some commercial tests contain antibodies that can identify the presence of antigens by binding to them. These types of tests can take less than an hour to complete, but may not be as accurate as viral culture.