The 100-day Cough "Pertussis"

Pertussis, or whooping cough, also known as the 100-day cough, is a highly contagious, vaccine-preventable bacterial disease, remains a concern worldwide. Globally, reported cases have fluctuated, with an average of 170,000 cases globally per year between 2010 and 2019. From 5-10% of all cases of pertussis are recognized and reported. A decline occurred during the COVID-19 pandemic due to reduced surveillance and contact rates. However, in 2023 and 2024, there has been an uptick in cases in certain regions, such as Europe and the Americas.

In 2024, reported cases of pertussis increased across the United States, indicating a return to more typical trends. Preliminary data show that more than six times as many cases have been reported as of week 47 reported on November 30, 2024, compared to the same time in 2023.

Transmission

Bordetella pertussis is transmitted through respiratory droplets expelled by an infected person during activities like coughing or sneezing. The bacteria are highly contagious and can spread easily in close-contact environments, such as schools or households.

Touching surfaces contaminated with respiratory secretions may contribute to transmission, though this is less common compared to airborne droplets.

Unvaccinated or partially vaccinated individuals are more susceptible. Infants, who are not fully immunized, are at the greatest risk. Waning immunity in adults and adolescents can contribute to outbreaks.

Infectivity

Pertussis is most contagious during the early catarrhal stage (the first 1-2 weeks of illness) when symptoms resemble a common cold. Infectiousness decreases but persists during the paroxysmal stage when severe coughing fits occur.

It is highly infectious and spreads mainly through respiratory droplets. Its infectivity is particularly notable in close-contact settings, such as households or schools.

Without antibiotic treatment, an individual can remain contagious for up to 3 weeks after the onset of the coughing stage.

The basic reproduction number for pertussis ranges from 12 to 17, indicating its high transmissibility compared to other respiratory infections like influenza.

Vaccinated individuals can still carry and spread the bacteria without showing symptoms, complicating efforts to control transmission. Infants and unvaccinated individuals are most at risk due to immature or absent immunity.

Causes of the Resurgence

The resurgence of pertussis (whooping cough) in certain regions can be attributed to multiple interconnected factors:

1. Decreased Vaccination Rates

• COVID-19 Pandemic Impact: During the pandemic, routine immunizations, including the DTP vaccine (diphtheria, tetanus, and pertussis), were disrupted globally. This caused a decline in vaccination rates, leaving many children unprotected.

• Vaccine Hesitancy: Misinformation about vaccines has contributed to lower vaccination uptake in some populations, affecting herd immunity.

2. Waning Immunity

• Immunity from the pertussis vaccine decreases over time. Both the whole-cell and acellular vaccines require booster doses to maintain protection, but gaps in booster vaccinations can leave populations vulnerable.

• Neither natural disease nor vaccination provides complete or lifelong immunity against pertussis reinfection or disease.

• Subclinical reinfection undoubtedly contributed significantly to immunity against disease ascribed previously to both vaccine and prior infection.

3. Epidemiological Shifts

• With fewer cases reported during the pandemic due to reduced interaction and better hygiene, susceptible individuals in the population increased, creating conditions for outbreaks once restrictions were lifted.

4. Vaccine Type

• The acellular pertussis vaccine, widely used due to its lower side effects compared to the whole-cell vaccine, provides shorter-lasting immunity. This contributes to an increased risk of infection in later years, especially among adolescents and adults.

5. Lack of Comprehensive Surveillance

• In some regions, pertussis surveillance systems are insufficient to detect and respond promptly to outbreaks. This results in underreporting and delayed public health actions.

Catarrhal Stage

Catarrhal stage (1-2 weeks) symptoms include runny nose, mild cough, sneezing, and low-grade fever. Symptoms mimic the common cold. This stage is the most contagious.

Paroxysmal Stage

Paroxysmal stage persists from 1 to 6 weeks and can extend longer. Symptoms include severe, spasmodic coughing fits (paroxysms), often followed by a "whooping" sound during inhalation, and vomiting after coughing. Exhaustion occurs due to frequent and intense coughing. Red or bluish discoloration of the face occurs during coughing episodes. Coughing episodes are more frequent at night. Infants may experience apnea (pauses in breathing) instead of a typical cough.

The Convalescent Stage

The convalescent stage of pertussis (whooping cough) typically lasts 2 to 6 weeks but can sometimes extend to several months. During this stage coughing fits gradually decrease in frequency and severity. Residual symptoms, such as a persistent mild cough, may linger for an extended period due to the damaged respiratory epithelium and prolonged immune response.

Older individuals and infants may experience a longer convalescent phase. Secondary infections, like pneumonia, can extend recovery. Individuals with weakened immune systems may have delayed symptom resolution. Though no longer contagious during this stage, the prolonged cough can cause significant discomfort and fatigue.

Patience and supportive care are crucial during recovery. Recovery is slow, and secondary infections like pneumonia may occur. Symptoms may be atypical, with minimal or no cough.

Complications of Pertussis

Pertussis can cause significant complications, particularly in infants, older adults, and individuals with weakened immune systems.

Respiratory complications of Pertussis include pneumonia, apnea, and bronchiectasis. Pneumonia is the most common and serious secondary infection. It accounts for many pertussis-related deaths, especially in infants. Respiratory failure may occur due to severe and prolonged coughing.

Seizures can occur due to oxygen deprivation during severe coughing fits. Encephalopathy is rare but serious; may result from hypoxia or pertussis toxin. Developmental delays may result from severe complications in infants.

Rib fractures may occur because of the intensity of coughing, particularly in adults. Abdominal or inguinal hernias may develop due to the strain from prolonged coughing.

Weight loss and dehydration may occur due to vomiting and exhaustion following coughing fits.

Infants are particularly vulnerable to cyanosis due to oxygen deprivation, failure to thrive from feeding difficulties during illness and increased risk of sudden death. Most pertussis-related deaths occur in infants under 6 months of age, often due to complications like pneumonia or encephalopathy.

Long-term effects include chronic cough that can last for months and increased susceptibility to other respiratory infections following pertussis.

Urgent Medical Attention

Seek immediate medical care if breathing difficulties occur, cyanosis or prolonged apnea is observed, particularly in infants, and severe dehydration or unresponsiveness develops.

Prevention

Effective prevention includes timely vaccination to prevent pertussis and its complications and public health measures like isolating suspected cases to reduce spread. Early diagnosis and antibiotic treatment can reduce the severity of the disease and prevent secondary infections. Close contacts, especially in households, are often given prophylactic antibiotics.

Try your best to keep your home free of any irritants that can trigger coughing, such as smoke, dust and chemical fumes. Use a clean, cool humidified mist to help loosen mucus and soothe the cough and practice proper handwashing. Drink plenty of fluids, including water, juices and soups, and eat fruits to prevent dehydration.