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Epidemiology of pertussis ( Whooping cough )
Identification
A highly contagious upper respiratory tract bacterial infection. Clinically has 3 stages; the
initial catarrhal stage is characterized by the insidious onset of coryza (runny nose),
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sneezing, low-grade fever, and a mild, occasional cough, similar to the common cold. The
cough gradually becomes more severe and irritating.
In the convalescent stage, recovery is gradual. The cough becomes less paroxysmal and
disappears over 2 to 3 weeks and vomiting stop . However, paroxysms often recur with
subsequent respiratory infections for many months after the onset of pertussis. Fever is
generally minimal throughout the course of pertussis.
Complication
B) Arise from increased pressure during attacks of paroxysmal cough and secondary
bacterial infection & malnutrition .
C) Pneumonia is a relatively common complication
D) Haemorrhages (subconjunctival, petechiae and epistaxis)
E) Convulsions.
F) Encephalopathies
G) Death occur more rarely ( in children less than 3 years ).
H) Complications are more frequent and severe in younger infants. Older persons
(adolescent and adults), and those partially protected by the vaccine usually have
milder disease.
Clinical case definition
1. A case diagnosed as pertussis by a physician, or
2. A person with a cough lasting at least 2 weeks with at least one of the following
symptoms:
3. Paroxysms of coughing.
4. Inspiratory “whooping”.
5. Post-tussive vomiting (vomiting immediately after coughing).
Case classification
Clinical case: A case that meets the clinical case definition.
Confirmed case: A clinical case that is laboratory confirmed (isolation of Bordetella
pertussis, by PCR, culture , or positive paired serology).
In infants, older vaccinated children,adolescents,and adults the clinical course may not
be typical , and prolonged coughing may be the only symptom.
In these cases, diagnosis of pertussis requires lab. Methods for confirmation
Infectious agent
Bacterium: Bordetella pertussis(small Gram-negative coccobacillus that infects the
mucosal layers of the human respiratory tract).
Occurrence
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An endemic disease common to children (especially young children), regardless of
ethnicity, climate or geographic location.
Outbreaks occur typically every 3 to 4 years cyclical disease.
In Iraq according to MOH report 2012 , the number of whooping cough cases were 2370
,the highest no. of cases was reported from Baghdad followed by Babylon.
Reservoir
Humans are the only host for pertussis.
Mode of transmission
direct contact with discharges from respiratory mucous membranes of infected persons
via the airborne route.
Even though the disease may be milder in older persons, these infected persons may
transmit the disease to other susceptible persons, including non-immunized or under-
immunized infants. Adults are often found to be the first case in a household with multiple
pertussis cases.
Incubation period
Average 9–10 days (range 6–20 days).
Period of communicability
Pertussis is highly communicable in the early catarrhal stage. Communicability gradually
decreases after the onset of the paroxysmal cough. Untreated patients may be
contagious for up to 3 weeks after the onset of paroxysmal cough in the absence of
treatment or up to 5 days after onset of treatment.
Susceptibility
Anyone who has not had pertussis previously or who has not received the pertussis
vaccine can get the disease.
Immunity following disease or vaccination is not lifelong. Older children, adolescents and
adults can become susceptible to pertussis five-to 10-years after their last dose of
pertussis-containing vaccine.
Begin at birth , no maternally acquired immunity.
The highest around school age (5-7) years and almost all become immune by the age of
15 years .
Sex incidence and fatality more in female than in males .
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Adults may occasionally be affected.
Methods of control
A) Preventive measures:
Active immunization by pertussis vaccine (killed vaccine) used in form of DPT for children
below 4 years.
DTP-containing multi-antigen vaccines (with Hep B, Hib, or IPV) are increasingly being
used in national immunization campaigns.
No single antigen pertussis vaccine is available.
Protective value : around 80% prevent the disease ,and lowers duration and severity
&fatality of disease in the vaccinated children
Pertussis vaccine must not be given to :
1. All children over 4 years .
2. At risk ,below 4 years.
cases of convulsion history given by the mother
History of epilepsy in 1
st
degree relative
Those showing adverse reaction after giving vaccine ,further doses should not be given
(give DT).
The reactions are :
1. Persistent crying lasting 3 hours or more or unusual high pitch cry occur within 48
hours.
2. Fever of 40C or greater within 24 hours.
3. Collapse or shock like state (hypotonic ) within 24 hours.
4. Acute encephalopathy within 7 days including sever alteration in consciousness with
generalized or focal neurological signs.
5. Convulsion with or without fever within 3 days.
Health education: of parents for basic knowledge of the disease & the protective value
and precautions with the vaccination.
Seroprophylaxis: antipertussis immunoglobulin 2.5 ml IM can be given to protect
susceptible contact , specially infants &young children . Protective value is not certain, So
chemoprophylaxis is preferred.
Chemoprophylaxis oral erythromycin or clarithromycin can be given in proper dosage, for
5 days after the last contact with the case to:
Infants & young children not actively immunized before.
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Susceptible school contacts .
Control measures (Case management)
Reporting to local health authority .
Isolation at home : practically difficult since the majority of cases are mild with no or slight
fever , they usually move in the community and go to school and spread infection to
exposed susceptible children .
Suspected cases who do not receive AB should be isolated for 3 weeks .
Erythromycin or clarithromycin should be administered for 14 days to all cases and close
contacts of persons with pertussis, regardless of age and vaccination status, 40 mg/kg/day
for children and 1 g/day for adults.
Drug administration both
(1) modifies the course of illness (if initiated early)
(2) eradicates the organism from secretions, thereby decreasing communicability.
Trimethoprim –sulfamthoxazole may be used in case of allergies
contacts
If the contact is an infant, should be separated From the patient, given prophylactic
erythromycin for 10 days.
If the infant cant be separated erythromycin should be given for the whole period of
communicability.
Child 3-4 years and has been immunized , should be given a booster dose as soon as
possible.
If the child has not been immunized ,should be given prophylactic erythromycin