Enhanced surveillance for pertussis (whooping cough)
Advisory Alert
June 24, 2016
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This is a reminder to consider pertussis in the differential diagnosis of patients presenting to you with signs and symptoms compatible with pertussis.
This reminder is in response to recent pertussis outbreaks occurring in the neighbouring communities of West Nipissing and Blind River, as well as an increased number of sporadic pertussis cases that have occurred locally over the past few weeks.
The Advisory Alert provides you with a brief summary of the local context of pertussis cases and information on pertussis etiology, clinical presentation and transmission, laboratory testing, clinical management, and vaccine considerations.
Local context
Since January 2016, a total of 11 pertussis cases have been reported to the Sudbury & District Health Unit. The last peak in incidence that occurred in the Health Unit’s service area was in 2012, when 19 cases were reported. This pattern was noted across the province. Pertussis outbreaks tend to be cyclical in nature, with increased disease activity approximately every 2 to 5 years. There is seasonal variation with increases in incidence observed primarily in winter and summer months.
Etiology, clinical presentation, and transmission
Pertussis is an infection of the respiratory system caused by the Bordetella pertussis bacterium. It is endemic worldwide and is vaccine preventable. Young infants ˂ 4 months of age have the highest risk of mortality. Risk is greatest before children are eligible to receive the vaccine or before completion of the primary vaccine series. Pertussis tends to be under-diagnosed, particularly among adolescents and adults.
Pertussis is primarily transmitted by the respiratory route through contact with respiratory droplets. The incubation period is 9 to 10 days (range 6 to 20 days), and could, rarely, be as long as 42 days. Infectiousness is divided into 3 stages:
- Catarrhal stage: characterized by mild upper respiratory tract symptoms with a mild occasional cough that lasts 1 to 2 weeks then progresses to the next stage;
- Paroxysmal stage: presents with an increase in the severity and frequency of the cough and lasts 1 to 2 months, sometimes longer; paroxysms are characterized by repeated violent coughs and this is where the high pitched inspiratory whoop may occur commonly followed by vomiting; fever is absent or minimal
- Convalescent stage: characterized by gradual recovery (up to several months) where the cough becomes less paroxysmal and disappears.
Pertussis is highly communicable during the catarrhal stage and during the first 2 weeks of the paroxysmal stage. Communicability gradually decreases and becomes negligible after three weeks.
Laboratory testing
Laboratory testing, using nasopharyngeal (NP) swabs, should only be done on patients with clinical signs and symptoms. Testing asymptomatic persons who are household contacts of a person with pertussis should be avoided as the PCR assay is very sensitive and detects low levels of DNA (e.g., even non-viable bacteria located in the nasopharynx). Thus the positive predictive value of the test will decrease in this situation. Asymptomatic close contacts of confirmed cases should not be tested and testing of contacts should not be used for post-exposure prophylaxis decisions. Optimal Timing for PCR Testing for pertussis is within three weeks of cough onset when bacterial DNA is present in the nasopharynx. The Public Health Ontario General Test Requisition can be found at:
Treatment
Treatment should be based on symptoms of early pertussis—efficacy is related to early treatment (unlikely beneficial after 21 days since initial contact). However, untreated symptomatic cases of pertussis whose PCR results are positive should be started on treatment regardless of time since symptom onset. Cases are not considered infectious after five days of treatment.
Treatment as outlined in the current Anti-infective Guidelines for Community-acquired Infections includes:
|
First Line |
Drug | Dosage |
| Erythromycin | Adults: 1-2 g/day divided BID, TID or QID | |
| Erythromycin estolate | Children: 30-40 mg/kg/day divided q6-8h for 7 days | |
| Clarithromycin | Adults: 250-500 mg BID
Children: 15 mg/kg/day divided BID |
|
| Azithromycin | Adults: 500 mg daily on first day; then 250 mg daily x 4 days
Children: 10 mg/kg/day on first day; then 5 mg/kg/day x 4 days |
|
| Second Line | TMP/SMX | Adults: 2 tabs BID or I DS tab BID
Children: 5-10 mg/kg/day divided BID |
Chemoprophylaxis
Current recommendations as per the Canadian pertussis control guidelines identify that chemoprophylaxis should only be provided to high risk contacts as soon as possible after exposure. Please call the Control of Infectious Diseases program using the contact information below for specific recommendations.
Vaccination considerations
The on time administration of the 2, 4, and 6 month doses of acellular pertussis vaccine is most critical in reducing infant mortality and hospitalization rates from pertussis. Up-to-date vaccine status varies with age. The current schedule for acellular pertussis vaccine is 2, 4, 6, and 18 months, 4 to 6 years, and 14 to 16 years. Adults should be considered up-to-date if they have had one adult dose. Please provide vaccine to all eligible persons who are not considered up-to-date.
Source: Ontario Agency for Health Protection and Promotion. Considerations for Public Health on Pertussis Case and Contact Management. September 2015.
Reporting
Pertussis is a reportable disease in Ontario. Report any suspected pertussis cases immediately to the Sudbury & District Health Unit for follow-up.
For all reporting, inquiries or comments, please call 705.522.9200, ext. 301.
Sincerely,
P. Sutcliffe, MD, MHSc, FRCPC
Medical Officer of Health
This item was last modified on September 9, 2016