As a parent, you may wonder whether you or your child with a cough has pertussis, but when you go to the doctor, he or she may not agree or even suggest testing.
The truth of the matter is that the accurate diagnosis of pertussis is challenging. Classic symptoms such as severe coughing spells and the inspiratory whoop are striking and strongly suggest pertussis, but they are not always present, especially in previously vaccinated or previously infected adolescents and adults. Additionally, as described in Dr. Cherry’s recent post, available tests are most sensitive early in disease when the bacteria is present in the nose, but this is often before pertussis is suspected. Accurate diagnosis also depends upon the likelihood of having been exposed to someone with pertussis. Communities across the U.S. are experiencing pertussis outbreaks and many children and adults present to their health care provider with a cough.
So, how do doctors know what to look for?
Pertussis occurs in ALL age groups but is most severe in young infants. While pertussis-containing vaccines have been available since the 1940s, pertussis outbreaks continue to occur every year in the U.S. The number of reported cases has been increasing steadily since the 1980s, especially among young infants and adolescents. According to the Centers for Disease Control and Prevention (CDC), more than 27,000 people were diagnosed with pertussis in 2010.
Pertussis is most severe in young infants who are too young to have received any or all doses of vaccine; in fact, about 3 of every 4 infants less than 6 months old develop complications like pneumonia or seizures and about 1 of every 100 infants less than 2 months old die. Unfortunately, many infants get pertussis from adolescents and adults who don’t realize that they have it.
Pertussis is transmitted in respiratory droplets by coughing and sneezing, and people with pertussis can be contagious for up to 3 weeks after developing symptoms. Pertussis is so contagious that when someone in the house has it, virtually everyone else in the house that is not immune will also get it. In fact, studies have shown that if ten unimmunized people are in a room with someone who is infected, 8 or 9 of them will also develop pertussis.
Vaccination is the most effective way to prevent pertussis, but protection is not lifelong. Vaccination is highly effective, however, it does not prevent all disease and immunity decreases over time. This is also the case after natural infection and is why even people who have had pertussis before should still get a booster dose. This decreased immunity through time is also why we have seen an increase in pertussis among adolescents and adults.
What Parents Should Look For
The official set of symptoms used to identify cases of pertussis is:
A cough that lasts for at least 14 days and either episodes of multiple, rapid coughs without any break, whooping when breathing in or a cough so severe that vomiting occurs.
However, it is important to realize that symptoms are not always typical, especially in previously vaccinated older children, adolescents and adults. The way that pertussis presents depends upon your age and vaccination status:
Infants and young children
The most ‘typical’ presentation occurs in young children:
- Stage 1 - Pertussis starts with mild cold symptoms like runny nose, mild cough and watery eyes This stage typically lasts for about 1 to 2 weeks.
- Stage 2 - Despite resolution of other symptoms, severe cough develops. ‘Whooping cough’ refers to episodes of multiple, rapid coughs without any break. The episodes can be so severe that the lungs run out of air resulting in a forced inhalation that sounds like a ‘whoop.’ The cough can also be accompanied by vomiting. Infants and children can look quite ill when coughing but appear well in between episodes. This stage can last for 1 to several weeks.
- Stage 3 – The coughing episodes begin to resolve and become less common over several weeks to months.
- All Stages – Fever is not a major symptom of pertussis.
Babies are less likely to show these classic symptoms. They tend to have coughing associated with gagging or gasping and ”apneic’ episodes, during which they briefly stop breathing. Infants and young children may also turn blue during coughing spells because they can’t get enough oxygen due to the severe, repeated coughing. Young infants may also show no interest in eating and might experience seizures.
If parents notice any of these signs or symptoms, they should have their child seen by a health care provider right away for testing and antibiotics—this is especially important for young infants since they are at the greatest risk for severe disease. Antibiotic treatment can decrease the duration of symptoms and make them less severe, but it is most effective when given early in the infection. Antibiotics also help decrease the likelihood of spreading pertussis to others.
Adolescents and adults
Older children, adolescents and adults with pertussis are more likely to have milder symptoms that can mimic other cough illnesses, especially if they have been immunized or previously infected, however, they can still develop severe disease:
- The primary symptom is often a persistent cough lasting at least 7 days, usually without a fever.
- Severe coughing episodes and whooping may occur, but is more common in unimmunized individuals.
- Coughing episodes can be severe enough to cause rib fractures, difficulty sleeping, poor bladder control, damage to the lung cavity and even bleeding in the brain. Vomiting with cough can also occur and is considered to be highly suggestive of pertussis in adults.
- The average duration of cough in adults is 1 to 1 1/2 months.
- Adolescents and adult who recently had pertussis may experience a return of symptoms if they get another respiratory infection shortly after recovering.
Because older children, adolescents and adults are less likely to have typical symptoms, they often are not tested or treated, and unknowingly spread pertussis to others. Pertussis should therefore be considered in anyone with a coughing illness with no fever or a mild fever, especially if they have been around someone with pertussis or a cough illness or they have regular contact with infants and young children who are at risk for severe disease.
A Final Word about Testing
Testing for pertussis is most sensitive in the first 3 to 4 weeks of infection. Bacteria that cause pertussis can usually be detected from the very beginning of the illness through the first two weeks of the cough stage; however, in people who have been vaccinated, like adolescents and adults, the bacteria may not be detectable for even that long. Since adolescents and adults often do not go to the doctor until late in their illness, there may no longer be any bacteria present. Therefore, choice of test is important:
- Bacterial culture is the gold standard but it is difficult to perform, takes a long time (up to 2 weeks) and is less likely to be positive later during the disease or in previously immunized individuals. It is most sensitive when performed within 2 weeks of cough onset.
- Pertussis PCR is now widely available, very sensitive and provides results quickly. Bacteria can be detected even 7 days after taking antibiotics, but false positives can also occur. PCR tests should NOT be done on anyone without symptoms, even close contacts of confirmed cases. PCR tests are most sensitive when done within 4 weeks of cough onset.
- Serology is a test that is performed on blood samples and detects antibodies to pertussis. This test is usually positive by the time a patient decides to see the doctor about a cough. However, because young infants don’t make antibodies to the protein that the test measures, it is not useful in infants. In people who were previously immunized, false positives may occur, so doctors need to look at relative levels of antibodies. This test is most useful in adults and adolescents because testing is usually done too late for culture or PCR tests. Serology testing can be performed within 2-8 weeks of cough onset. If the test is done too early in the infection, it may be falsely negative.
Parents who suspect pertussis in themselves or their children should discuss their concerns with their healthcare providers. Providers should be able to help in determining the best approach for making a diagnosis and managing treatment.
Kristen A. Feemster, MD MPH MSHP
Assistant Professor of Pediatrics
Pereleman School of Medicine at the University of Pennsylvania
Attending Physician, Division of Infectious Diseases
Physician-Scientist at the Vaccine Education Center
The Children’s Hospital of Philadelphia