What is Pertussis? Risk Factors, Pathogenesis, Early Specific Symptoms, and Treatment Options

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Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis.

What is Pertussis? Pertussis is a bacterial infection of the respiratory system characterized by severe coughing fits. It primarily affects infants and young children but can also affect adolescents and adults.

Pertussis can occur in people of all ages, but it tends to be most severe in infants and young children. The incidence of pertussis can vary depending on factors such as vaccination rates, population density, and access to healthcare.

In terms of racial diversity, pertussis can affect individuals of any race or ethnicity. However, disparities in healthcare access and vaccination rates may impact the prevalence of the disease within different racial or ethnic groups.

Regional variations in pertussis prevalence can occur due to factors such as population density, climate, and public health practices. Outbreaks of pertussis may occur in communities with low vaccination rates or where the protective immunity conferred by vaccination has waned over time.

Maintaining high vaccination coverage, especially among vulnerable populations such as infants and young children, is essential for reducing the prevalence of pertussis and preventing its complications. Regular booster doses for adolescents and adults can also help maintain immunity and reduce transmission within the community

Mortality Rate for Pertussis Infection: The mortality rate for pertussis infection can vary depending on several factors, including age, access to healthcare, and the presence of underlying health conditions. Historically, before the widespread availability of vaccines and modern medical treatment, pertussis could be associated with significant mortality, especially among infants and young children. However, with advancements in medical care and vaccination efforts, the mortality rate for pertussis has decreased significantly in many parts of the world.

In developed countries with access to healthcare and vaccination programs, the mortality rate for pertussis is relatively low, especially among older children and adults. However, infants, particularly those too young to be fully vaccinated, remain at higher risk of severe complications and death from pertussis infection.

Historical Mortality Rates for Pertussis: Historically, before the introduction of widespread vaccination programs, pertussis was a major cause of morbidity and mortality, especially among infants and young children. In the pre-vaccine era, pertussis outbreaks could result in significant numbers of severe cases and deaths, particularly during epidemics.

For example, in the early to mid-20th century, before the introduction of pertussis vaccines, pertussis was a leading cause of childhood mortality in many countries. Mortality rates during pertussis epidemics could vary widely depending on factors such as access to medical care, nutritional status, and the virulence of circulating strains of the bacterium.

Since the introduction of pertussis vaccines, including the DTaP (diphtheria, tetanus, and acellular pertussis) vaccine, mortality rates from pertussis have declined significantly in many parts of the world. Vaccination efforts have played a crucial role in reducing the burden of pertussis-related morbidity and mortality, particularly among infants and young children

Risk Factors: Risk factors for pertussis include being unvaccinated or incompletely vaccinated, close contact with someone infected with pertussis, and living in crowded conditions.

Pertussis remains a threat in regions or countries where vaccination coverage is low or where there are gaps in immunization programs. Additionally, areas with limited access to healthcare and resources for early diagnosis and treatment may also experience higher rates of pertussis transmission and associated complications.

Some regions where pertussis continues to be a concern include:

  1. Developing countries with limited access to healthcare infrastructure and vaccination programs. In these regions, pertussis can pose a significant threat to infants and young children, especially those who are not fully vaccinated.
  2. Communities with low vaccination rates or vaccine hesitancy. In some areas, concerns or misinformation about vaccines can lead to lower vaccination rates, increasing the risk of pertussis outbreaks and transmission.
  3. Regions experiencing conflict or humanitarian crises. Displacement, overcrowding, and disruptions to healthcare services can exacerbate the spread of infectious diseases like pertussis.
  4. Communities with suboptimal vaccine coverage or where immunity has waned over time. Even in developed countries with robust healthcare systems, localized pockets of low vaccination coverage can lead to pertussis outbreaks.

Pathogenesis: Bordetella pertussis attaches to the lining of the airways in the respiratory tract, producing toxins that damage the cilia (tiny hair-like structures) and cause inflammation, leading to the characteristic symptoms of the disease.

Link to Human Receptors: Bordetella pertussis attaches to and infects the respiratory tract epithelial cells, primarily through interactions with specific receptors on the surface of these cells. One key receptor involved in the attachment of Bordetella pertussis is the tracheal cytotoxin (TCT) receptor, which facilitates bacterial adherence to the respiratory epithelium.

Initial Targets in the Respiratory Tract: Upon inhalation, Bordetella pertussis primarily targets the ciliated epithelial cells lining the upper respiratory tract, including the trachea, bronchi, and bronchioles.

Entry into Endothelial Tracts: When Bordetella pertussis enters the endothelial tracts of the upper respiratory system, it adheres to and colonizes the respiratory epithelial cells. This colonization leads to the release of toxins by the bacterium, which disrupts the normal function of the respiratory epithelium and triggers inflammation.

Immune Evasion and Activation: Bordetella pertussis employs various strategies to evade and manipulate the host immune response. The bacterium can evade detection by immune cells through mechanisms such as inhibiting phagocytosis and interfering with the production of antibodies. Additionally, Bordetella pertussis produces toxins, such as pertussis toxin, adenylate cyclase toxin, and tracheal cytotoxin, which modulate immune cell function and contribute to the pathogenesis of pertussis.

Immune Response: The immune response to Bordetella pertussis infection involves both innate and adaptive immune mechanisms. Innate immune cells, such as neutrophils, macrophages, and dendritic cells, are recruited to the site of infection and play a role in clearing the bacterium. Adaptive immune cells, including T cells and B cells, are activated to produce specific antibodies and generate memory responses against Bordetella pertussis.

Reliability of Immunity: While immunity following natural infection or vaccination with pertussis vaccines is generally robust, long-term immunity to Bordetella pertussis may wane over time. This can result in susceptibility to reinfection or breakthrough infections, particularly in adolescents and adults who may not have received recent booster doses of pertussis-containing vaccines.

Allergic Reactions: Bordetella pertussis infection can trigger inflammatory responses in the respiratory tract, leading to the release of histamine and other inflammatory mediators. While pertussis itself does not typically induce broad allergic reactions, the inflammatory response to infection can contribute to symptoms such as airway hyperreactivity and bronchoconstriction in susceptible individuals.

The interaction between Bordetella pertussis and the host immune system is complex, involving both evasion and activation of immune responses. Understanding these processes is crucial for developing effective strategies for the prevention and treatment of pertussis

Causative Agent: The bacterium Bordetella pertussis is the causative agent of pertussis.

Genus and Specifications: Bordetella pertussis belongs to the genus Bordetella, which includes several other species of bacteria, such as Bordetella parapertussis and Bordetella bronchiseptica. However, Bordetella pertussis is the primary causative agent of pertussis in humans.

As for the natural reservoir of Bordetella pertussis, humans are considered the primary reservoir for the bacterium. Pertussis is a human-adapted pathogen, meaning it primarily circulates among human populations. Unlike some other infectious diseases, there is no known animal reservoir for Bordetella pertussis. Therefore, efforts to control pertussis transmission focus on vaccination, early diagnosis, and appropriate treatment in human populations

Transmission: Pertussis is highly contagious and spreads through respiratory droplets when an infected person coughs or sneezes.

Airborne Transmission: As an aerogenic bacterium, Bordetella pertussis can spread through respiratory droplets generated by coughing, sneezing, or talking. While the exact distance Bordetella pertussis can travel on airborne particles varies depending on factors such as humidity and airflow, it can potentially travel several feet in the air.

How to Suspect: Pertussis should be suspected in individuals, especially infants and young children, who present with prolonged coughing fits, particularly if followed by a characteristic “whoop” sound when breathing in.

Incubation Period: The incubation period for pertussis is typically 7 to 10 days but can range from 4 to 21 days.

Bordetella pertussis does not typically lie dormant in the body like some other pathogens such as Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). Instead, pertussis typically causes an acute infection characterized by symptoms such as severe coughing fits.

However, it is possible for someone to be infected with Bordetella pertussis and have very mild or even asymptomatic symptoms, especially in older children and adults who may have partial immunity from previous vaccinations or exposure. In such cases, individuals may not realize they are infected and may unknowingly transmit the bacterium to others.

In contrast to TB, where the bacterium can remain dormant in the body for years and then become active when the immune system is weakened, Bordetella pertussis does not have a dormant phase. Once a person is infected, the bacterium typically colonizes the respiratory tract and causes symptoms within a relatively short period.

However, it’s important to note that while someone may have mild or asymptomatic pertussis, they can still spread the infection to others, including individuals who may be more vulnerable to severe complications, such as infants who are too young to be fully vaccinated. Therefore, maintaining high vaccination coverage and practicing good respiratory hygiene are crucial for preventing the spread of pertussis within communities

Early Specific Symptoms:

Early symptoms of pertussis may resemble those of a common cold, including runny nose, sneezing, low-grade fever, and a mild cough. However, the cough gradually becomes more severe and develops into prolonged coughing fits.

In adults who have partial immunity from previous vaccinations or exposure to Bordetella pertussis, the symptoms of pertussis infection may be less severe compared to infants and young children. However, adults can still develop typical symptoms of pertussis, albeit milder in intensity.

Common symptoms of pertussis in adults may include:

  1. Persistent cough: A cough that gradually worsens over time and becomes severe, often characterized by coughing fits.
  2. Paroxysmal coughing: Coughing fits that may be accompanied by a characteristic “whoop” sound when inhaling.
  3. Posttussive vomiting: Vomiting that occurs after coughing fits.
  4. Fatigue: Feeling tired or exhausted, especially due to interrupted sleep from coughing fits.
  5. Respiratory symptoms: Runny or congested nose, sneezing, and mild fever.

Because the symptoms of pertussis in adults can resemble those of other respiratory infections, such as the common cold or bronchitis, the condition may go undiagnosed or be mistaken for a different illness

Timeframe for Developing Severe, Life-Threatening Symptoms to Death: The timeframe for developing severe, life-threatening symptoms of pertussis to death can vary depending on the individual’s age, overall health, and the severity of the infection. In severe cases, complications such as pneumonia, seizures, or respiratory failure can develop rapidly, leading to death within a matter of days to weeks after the onset of symptoms.

In infants, who are particularly vulnerable to pertussis complications, the progression from exposure to severe symptoms and potential death can be relatively rapid, especially if the infection is not promptly diagnosed and treated. However, with appropriate medical care, including supportive therapy and antibiotics, the risk of death can be significantly reduced.

Complications:

Pertussis, especially in younger children, can pose significant risks due to its effects on the respiratory system. One of the potential complications of severe pertussis infection is the risk of occlusion of the upper bronchial tree, particularly in infants and young children.

When the respiratory epithelial cells become inflamed and swollen due to Bordetella pertussis infection, it can lead to narrowing of the airways, especially in the smaller bronchioles. In severe cases, this inflammation and swelling can result in partial or complete obstruction of the upper bronchial tree, making it difficult for air to flow into the lungs.

In infants and young children, whose airways are already narrower compared to adults, this obstruction can be particularly dangerous. The inability of the bronchial canal to hold the inflamed surrounding tissues can lead to increased resistance to airflow, respiratory distress, and potentially life-threatening complications such as hypoxia (low oxygen levels) and respiratory failure.

Additionally, the characteristic coughing fits associated with pertussis can exacerbate the inflammation and swelling of the respiratory tract, further increasing the risk of airway obstruction. In severe cases, pertussis-related complications such as pneumonia and respiratory distress syndrome can also contribute to the risk of mortality, especially in infants and young children with underdeveloped immune systems.

Early recognition and prompt treatment of pertussis in infants and young children are essential for reducing the risk of severe complications and mortality. This may include supportive care, such as supplemental oxygen and hydration, as well as antibiotic therapy to reduce the severity and duration of symptoms and prevent transmission to others.

Vaccination against pertussis, starting with the DTaP vaccine in infancy and followed by booster doses in childhood and adolescence, is the most effective way to prevent pertussis infection and its associated complications, including the risk of airway obstruction and mortality. Ensuring high vaccination coverage within communities is crucial for protecting vulnerable populations, such as infants and young children, from the severe consequences of pertussis infection

How to Diagnose:

Diagnosis of pertussis is often based on clinical symptoms and confirmed through laboratory tests, such as PCR (polymerase chain reaction) to detect the presence of the bacteria in respiratory secretions.

If pertussis is left untreated, it can lead to various complications, especially in infants and young children. Some potential complications include:

  1. Pneumonia: Bacterial pneumonia can develop as a secondary infection due to damage to the respiratory tract caused by pertussis.
  2. Ear Infections: Middle ear infections (otitis media) are common complications of pertussis, leading to pain and potential hearing loss.
  3. Seizures: The severe coughing fits associated with pertussis can sometimes trigger seizures.
  4. Apnea: Infants, particularly those under six months of age, may experience episodes of apnea (brief pauses in breathing) during coughing spells.
  5. Brain Damage: In rare cases, severe and prolonged coughing fits can lead to brain damage due to oxygen deprivation

Treatment Options:

Treatment typically involves antibiotics, such as azithromycin, clarithromycin, or erythromycin, to reduce the severity and duration of symptoms and prevent transmission to others.

Gold Standard Drug: Erythromycin has traditionally been considered the gold standard for pertussis treatment. However, due to concerns about side effects and antibiotic resistance, azithromycin is often preferred, especially in children.

Prevention Strategies: Prevention of pertussis involves vaccination, maintaining good respiratory hygiene (covering mouth and nose when coughing or sneezing), and avoiding close contact with infected individuals.

Importance of DTaP Vaccine: The DTaP vaccine is crucial in preventing pertussis, as well as diphtheria and tetanus. It is administered in a series of doses to infants and young children and provides immunity against pertussis, reducing the risk of severe illness and transmission within the community

Regarding the management regimen to prevent outbreaks in cases where adults with partial immunity may still contract pertussis, several strategies can be implemented:

  1. Vaccination: Ensuring that adults are up to date with their pertussis vaccinations can help boost immunity and reduce the risk of infection and transmission. Booster doses of the Tdap vaccine (tetanus, diphtheria, and acellular pertussis) are recommended for adults every 10 years.
  2. Early diagnosis and treatment: Prompt diagnosis and treatment of pertussis in adults can help reduce the severity and duration of symptoms, as well as limit the spread of the infection to others. Antibiotics, such as azithromycin, clarithromycin, or erythromycin, are typically prescribed to treat pertussis.
  3. Respiratory hygiene: Practicing good respiratory hygiene, such as covering the mouth and nose when coughing or sneezing, can help prevent the spread of pertussis to others.
  4. Contact tracing and immunization of close contacts: Identifying and immunizing close contacts of individuals with pertussis can help prevent further transmission within communities, especially among vulnerable populations such as infants and young children.

By implementing these management strategies, outbreaks of pertussis can be minimized, and the impact of the disease on public health can be reduced

ICD-10: A37.9 (033.9)

Verified by: Dr.Diab (July 10, 2024)

Citation: Dr.Diab. (July 10, 2024). What is Pertussis? Risk Factors, Pathogenesis, Early Specific Symptoms, and Treatment Options. Medcoi Journal of Medicine, 4(2). urn:medcoi:article33708.

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