If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Pertussis diagnosis and treatment

Want to join the conversation?

Video transcript

- [Woman] Before we talk about how to diagnose Pertussis, also called Whooping Cough, let's review the timeline of the stages that occur during the bacterial infection. From the time the first common cold symptoms occur to about two weeks, the bacteria that causes Pertussis is in the upper respiratory tract. It's thriving, and it's causing damage and inflammation in the airways. And in about two weeks, this damage is significant enough to cause mucous to build in the airways, and it triggers a coughing fit, with whooping when breathing in, and vomiting after fits. At the same time, the body's finally been able to make antibodies specific for Pertussis, which tag the bacteria for destruction by the immune system. So that means that at about eight weeks into the infection, the immune system's been able to clear the infection, and the damage and inflammation in the airways can begin to heal over the next four weeks, which means the symptoms will slowly go away. Now the timeline's important because there's a few ways to diagnose Pertussis, but which way is used depends heavily on the stage in the infection. The gold-standard test for diagnosing Pertussis can only be done in the first two weeks of the symptoms, when the bacteria's still alive. So let's mark off the two weeks and write in that the test is a swab. And to test the patient, a healthcare worker would take protective cautions, wear a gown, gloves, and a mask to prevent being infected, and then swab the back of the patient's nasopharynx with a polyester, Dacron-tipped swab. Then it's brought back the lab, and if Pertussis is present, it'll multiply and grow, like I'm drawing here, within seven to eight days. And positive results are really accurate, but negative results don't rule out an infection's occurred, because a sample may not have been taken during the correct stage, or with the right technique. So this test is often used in combination with another test that confirms results. A polymerase chain reaction can be performed any time up to four weeks. It's often just abbreviated and called a PCR, so P C R. And it can be done on the same swab sample, because it tests only for the presence of the Pertussis DNA. If Pertussis DNA is present, the PCR will make millions of copies of a specific portion, and these copies can be detected in lab to confirm a Pertussis infection. Now, because the DNA can come from live or dead bacteria, testing's possible up to four weeks, when the bacteria's mostly dead. And the results are fast, they take about one to two days, but they can sometimes give positive results that are actually false if the sample is contaminated. So that's why it's typically done in combination with growing Pertussis in the lab. And finally, I want to include one last test that exists, because it's the only one that can be performed from weeks two to 12, which is pretty late into the course of the disease. It's serology, and this test detects antibody levels in the blood. So here's some Pertussis bacteria, and at about two weeks, the body starts producing these antibodies that are specific to tag Pertussis for destruction by the immune system. So because antibody levels are at their highest between weeks two and eight, when the body's in the middle of fighting Pertussis, this is an ideal time to have the serology test done. But, since antibody levels will slowly taper off once the infection is cleared, they can still be detected all the way into the 12th week. One of the technical challenges with this test is that if a person has recently been vaccinated, antibody levels in the blood will be high, and this will give positive test results, even if a natural infection hasn't occurred. For this reason, and a few other technical challenges, the test isn't widely available, and it's not a preferred diagnostic tool, but it's something to keep in mind because it's being developed and fine-tuned for general use. Now that we've covered the lab tests, lets talk about how clinical diagnoses of Pertussis can be made. If for two weeks or longer a patient's experiencing coughing fits, whooping, or vomiting after coughing, without any other known cause, Pertussis can be diagnosed. And while I drew this line during the second stage when the symptoms would normally develop, a diagnoses can be made earlier, and in less time, if it's known a person has been exposed to a person with a Pertussis diagnoses. And let's say a person is diagnosed with Pertussis, what do we do next? Well, let's slide this up, and let's say a patient's diagnosed with Pertussis early in the first two weeks of the initial symptoms. During this time, macrolide antibiotics can be prescribed to make future symptoms more mild, but the antibiotics won't be useful after this time, because remember, past this point, the damage and the inflammation from the infection's already occurred, and it'll still lead to the symptoms in the other stages. But if an uninfected person has been exposed to a person with a Pertussis diagnoses, they can begin taking antibiotics immediately during this seven to 10 day incubation period. And by doing this, the antibiotics will help prevent the damage and the inflammation and make symptoms more mild if they occur at all. But really, mostly the treatment for Pertussis is managing the symptoms, so for the cough, a patient can use a humidifier to hydrate the mucous to make it easier to cough up, and a patient would benefit from avoiding activities that might trigger additional coughing, so avoid running, dusty locations, things like that, but we don't want to eliminate the cough altogether, because it's still needed to help remove the mucous from the airways. So over-the-counter cough suppressants are not recommended. Plenty of rest is a good idea, though, to save up energy for the tiring coughing fits when they do come. And to prepare for the vomiting, which commonly occurs after coughing fits, patients should pay attention to proper nutrition by staying hydrated and eating small, frequent meals. In infants younger than one year old who tend to have severe symptoms, this may mean they need some extra help at the hospital through IV hydration and passing a tube down their throat to their stomach to get food in. If a patient starts having trouble breathing, administering oxygen may be necessary. Symptoms of troubled breathing, or respiratory distress, are low oxygen and increased heart and breathing rate. And finally, patients should be monitored for the development of additional respiratory infections in addition to Pertussis, because Pertussis infections cause mucous to build in the lungs, and it creates this perfect environment for other bacteria to survive and thrive. So monitoring for this can be done with chest x-rays, since Pertussis is not typically visible on x-rays, but other infections may appear as white areas in the lungs that would normally be black.