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EPIDEMIOLOGY AND CONTROL OF WHOOPING COUGH. DR. REEMA KUMARI Associate professor Department of community medicine and public health K.G. Medical University, Lucknow. Pertussis (History). The earliest clear account of whooping cough was described in 1640 by Baillow , an epidemiologist
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EPIDEMIOLOGY AND CONTROL OF WHOOPING COUGH DR. REEMA KUMARI Associate professor Department of community medicine and public health K.G. Medical University, Lucknow
Pertussis (History) • The earliest clear account of whooping cough was described in 1640 by Baillow, an epidemiologist • The name ‘pertussis’ means “violent cough”, and was first used to describe the disease in 1679. • In China, the disease is known as “Hundred Day Cough”
Pertussis • An acute infectious disease, usually of young children caused by B.pertussis. • Insidious onset with mild fever and an irritating cough gradually becoming paroxyamal with the characteristic “whoop”
Pertussis (Bacteriology) • Pertussis toxin and filamentous hemagglutinin (FHA) allow binding of pertussis to respiratory epithelial cells. • PT can then enter the bloodstream.
Pertussis (Epidemiology) • Pertussis is a disease of worldwide importance, with an estimated 285,000 deaths in 2001, with most occurring in Africa and SE Asia • According to the WHO,2010 there are 1.29 lacs cases reported globally, with 95% occurring in developing countries, and the DPT(3) Immunization rate was 85%. • In India yr.1987 incidence was 1.63 lacs cases, in 2011only 39,091 cases were reported (decline of 76%)
Epidemiological determinants • AGENT FACTORS • B. pertussis is very contagious, and attack rates among susceptible groups range from 50-100% depending on the nature of the exposure. • B. pertusis occurs in smooth and rough phases, capsulated and non-capsulated form, elaborates an exotoxins and endotoxins • B. pertusis is antigenically highly complex. It carries 3 major agglutinogens-1,2,3 and several minor ones • Survives only for very short periods outside the human body
HOST FACTORS AGE: disease of infants and pre-school children; however, children under the age of 5 years are at the highest risk of developing more serious symptoms. Being in close contact with an infected person for extended periods of time increases the risk of becoming infected IMMUNITY: recovery from whooping cough or adequate immunization is followed by immunity. Infants are susceptible to infection from birth bec. Maternal antibody does not appear to give them protection. no cross immunity with B. Parapertussis
Source of infection • B. pertusis infects only man, source is a case of pertusis • Transmission is felt to occur by aerosol droplet, and exposure to a coughing patient. • There are no known animal reservoirs for B pertussis, and the organism does not survive for prolonged periods in the environment. • No long-term carrier state had been identified, but asymptomatic culture positive persons can be detected during known exposures.
Infective material • The bacilli occurs abundantly in the nasopharyngeal and bronchial secretions, which are infective • Objects freshly contaminated by such discharges are also infective
Infective period • Whooping cough is most infectious during catarrhal stage. • The infective period may be considered to extend from a week after exposure to about 3 weeks after the onset of paroxysmal stage
Whole cell pertussis vaccine has been responsible for a major reduction in disease incidence, but has caused a shift in the peak age of disease.
CLINICAL COURSE Stage 1 (Catarrhal): • Cold, runny nose and irritating cough • Most infectious stage Stage 2 (Paroxysmal): • Severe series of coughs usually ending with a high-pitched whoop • The whoop starts 1 to 2 weeks after the cold symptoms and lasts 1 to 2 months • Thick, clear, sticky mucous may be coughed up at the end of the coughing spasm • Coughing spasms are more frequent at night
Stage 3 (Convalescent): • Gradual disappearance of symptoms occurring over 2 to 4 weeks, however, coughing spells can last for weeks or months • Cough may become louder and may sound like it is getting worse as the person is getting better • Coughing may flare up again later in a cold or upper respiratory illness. This does not mean that the person has been re-infected with pertussis
Pertussis (Clinical Manifestations) • After an incubation period of 1-3 weeks, signs and symptoms of the catarrhal phase begin • Symptoms include rhinorrhea, lacrimation, conjunctival injection, malaise, low grade fever, and are indistinguishable from those of many other URI’s. • After a few days and up to a week of these symptoms, a dry nonproductive cough develops, and this evolves into a characteristic paroxysmal phase.
Patients are most contagious during the catarrhal phase and during the first two weeks after the onset of coughing. • Prodromal symptoms during this phase can include complaints of pharyngeal discomfort. • During this phase, patients can develop a marked leukocytosis, with WBC counts greater than 50,000, with a relative lymphocytosis (less common in adults).
The cough paroxysm consists of a short series of expiratory bursts, followed by an inspiratory gasp, which results in the typical “whoop”. • The paroxysmal phase usually lasts 1-6 weeks, but can last up to 10 weeks • Not all children with pertussis exhibit the characteristic whoop, and it is fairly uncommon in infants, who may have apneic episodes
In adults, whooping is variable, ranging from 20-40% in various studies. The disease is generally milder, but the paroxysmal cough may be just as prolonged. • Paroxysms can number more than 30 per 24 hours, and are more frequent at night, and can be stimulated by external stimuli, such as noises or cold air.
Classically they may end with a vomiting episode. They can be associated with sweating, flushing and syncope. Patients may cough up thick yellow plugs. • Pertussis is generally more severe in infants, but presentation can be more atypical in infants, as well as partially immunized children and previously immunized adolescents and adults. • In these groups the catarrhal phase can be shortened, and the true whooping phase may be absent.
The convalescent phase begins with a decrease in the intensity of the cough and paroxysms, but can still last for weeks. • It is not clear if pertussis can cause long term impairment of pulmonary function.
COMPLICATIONS • Complications occurs in 5-6 percent of cases • The chief complications of pertussis are bronchitis, bronchopneumonia and bronchiactasis • secondary infections-otitis media or pneumonia (either secondary to pertussis or other organisms) • Aspiration can occur secondary to the whooping and associated gasping
Patients can develop subconjunctival hemorrhages, epistaxis, haemoptysis and punctate cerebral haemorrhages which may cause convulsions and coma • CNS abnormalities can occur particularly in children 6 months and younger.
Direct fluorescent antibody tests (DFA) are often used as well, but they can be less sensitive and less specific, and may lead to overdiagnosis and overtreatment (higher false positives from cross reaction with normal naso-pharyngeal flora). • With new PCR technology becoming available, the ability to diagnose Bordetella infection has been greatly enhanced
A clinical case is defined as a cough illness lasting at least 2 weeks without other apparent cause accompanied by one of the following • Paroxysms of coughing • Inspiratory ‘whoop’ • Posttussive vomiting
Pertussis (Treatment) • The newer macrolides (azithromycin and clarithromycin) have good in vitro acitivity against B pertussis, and Clarithromycin (500 mg bid) used for 10 – 14 days and Azithromycin (500 mg/d) used for 5 – 7 days have been used with good results.
Steroids may reduce the number and severity of cough paroxysms, but are generally only recommended for infants with serious disease.
Pertussis (Control & Prevention) • Antibiotics can be used for 2 purposes in the control and prevention of pertussis : • Treatment to modify clinical symptoms of pertussis by administering to symptomatic patients
Prevention of secondary spread of pertussis by administering to: • Symptomatic patients (treatment) and interrupting infectiousness and transmission by eliminating the organism from the respiratory system. • Asymptomatic contacts (prophylaxis) and interrupting transmission by eliminating any organisms that may have been contracted
Are there other ways to prevent Pertussis? • Other methods of preventing the spread of Pertussis include: • Washing hands with soap and warm water. • Teaching children to cover mouth and nose if coughing or sneezing and to wash hands after doing so. • Not sharing eating utensils and drinking glasses. • Minimizing the amount of contact you have with someone you know is infected or if you are infected, minimizing the amount of time you are around others.
