With pertussis cases on the rise, it's time to brush up on best practices for diagnosing, treating, and containing this highly contagious respiratory infection. Aside from thinking of the song, “Whoop there it is” whenever I hear pertussis, and the fact that it’s one of the only things Azithromycin is still good for, the rest of the details about this disease were buried in the back of my brain!
Pertussis: What We’re Up Against
Pertussis, or whooping cough, is caused by Bordetella pertussis, a highly infectious bacterium that spreads through respiratory droplets. One infected household member? There’s an 80% chance the rest will catch it! Worldwide, pertussis is endemic, and cases peak cyclically—most often in late summer and fall, though it can strike year-round. With the incubation period averaging 7-10 days, many patients may already be contagious by the time they seek care.
Phases of Pertussis
Pertussis has three distinct phases:
Catarrhal Phase (1-2 weeks): The infection starts like a cold, with a mild cough, runny nose, and watery eyes. The fever is either low or absent. This is the most contagious phase and the easiest to miss unless there’s a known exposure.
Paroxysmal Phase (several weeks): Coughing intensifies, often leading to prolonged fits ending with a classic “whoop” as patients gasp for air. Post-cough vomiting and color changes in infants are common.
Convalescent Phase (weeks to months): Though no longer contagious after 21 days from onset, the cough may persist (avg 6-10 weeks), which explains pertussis’s infamous “100-day cough” reputation.
Do We Worry About Vaccinated Patients?
Immunity from pertussis vaccines isn’t lifelong. Studies suggest that protection wanes about four years after the last dose, making even vaccinated individuals susceptible. Infants, who are often incompletely vaccinated, remain the highest-risk group for severe illness, with an increased risk of fatality, apnea, pneumonia, and even seizures.
Quick Hit! Pertussis is one of the leading causes of vaccine-preventable deaths worldwide!
How to Diagnose
When pertussis is suspected, testing is beneficial for two main reasons: confirming diagnosis and guiding decisions about treating close contacts. PCR testing is the go-to, given the faster turnaround and improved sensitivity over traditional culture.
Chest X-rays?
Routine chest X-rays aren’t recommended for straightforward cases of pertussis. They’re typically normal in uncomplicated cases and rarely add diagnostic value. If patients show signs of severe respiratory distress or other complications, chest imaging might be appropriate, but not as a standard workup.
Treatment Considerations
When treating pertussis, clinical suspicion often determines whether you start antibiotics before confirmatory results are available. In high-risk cases (like infants or those with known exposures), it’s appropriate to start treatment right away and discontinue if tests return negative.
Drug of Choice? For both treatment and prophylaxis, Azithromycin takes center stage. The recommended 5-day course is not only effective but also straightforward in dosing, especially for pediatric patients. Alternatives include clarithromycin, erythromycin, and trimethoprim-sulfamethoxazole.
Patient Education is Key
Managing expectations is one of the more important counseling points for patients and families. Treatment often does not shorten the duration of cough, especially when patients are already in the paroxysmal phase. In fact, the primary reason we treat is to reduce transmission risk, not to eliminate symptoms. So, when antibiotics are prescribed, it’s crucial to clarify that they’re meant to protect others, not necessarily resolve the patient’s cough.
Prophylaxis: Who Needs It?
Given the highly contagious nature of pertussis, prophylactic treatment is recommended for:
All household contacts within 21 days of symptom onset.
High-risk contacts—particularly infants under 1 year, immunocompromised individuals, and those with significant respiratory conditions.
Contacts of high-risk individuals (like healthcare workers in NICUs or maternity wards) who may have been exposed.
An asymptomatic child from school with an isolated exposure? They typically don’t need prophylaxis. However, testing and treatment become essential if any close contacts develop a cough after exposure.
Reporting and Isolation Protocols
Clinicians should report confirmed or suspected pertussis cases to their local public health departments, which helps in tracking and managing community spread. Isolation guidelines are straightforward: symptomatic patients should be isolated until they’ve completed five days of antibiotic treatment or until 21 days post-onset if untreated. For exposed individuals, isolation guidance is less clear, but household contacts should avoid high-risk individuals for 21 days post-exposure if prophylaxis isn’t feasible.
Interested in learning more? Check out the Pertussis episode of Urgent Care Reviews and Perspectives, where Tiffany Proffitt, DO, and Karen Hovav, MD, discuss all things pertussis!