Enhanced Surveillance for Pertussis (whooping cough)

Advisory Alert

July 4, 2018

*  Cette information est seulement disponible en anglais.

To health care providers and community partners:

Please be advised that there has been recent pertussis activity occurring in the neighbouring community of Powassan and the surrounding area. Please consider pertussis in the differential diagnosis of patients presenting to you with signs and symptoms compatible with this infection. Pertinent information regarding pertussis is summarized below.

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. 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:

1. 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.
2. 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.
3. 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:
https://www.publichealthontario.ca/en/ServicesAndTools/LaboratoryServices/Pages/Requisitions-and-forms.aspx.

Treatment

Macrolide antibiotics such as azithromycin and erythromycin may prevent or moderate clinical pertussis when given during the incubation period or in the early catarrhal stage. During the paroxysmal phase of the disease, antibiotics may not shorten the clinical course but may reduce the possibility of complications. Antibiotics eliminate the organism after a few days of use and thus reduce transmission. Untreated symptomatic cases of pertussis whose PCR results are positive should be started on treatment regardless of time since symptom onset.

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, it is unlikely beneficial after 21 days since initial contact.

High risk contacts include:

• Household contacts (including attendees at home day care) where there is a vulnerable person defined as an infant ˂ 1 year of age [immunized or not] or a pregnant woman in the third trimester.
• Non-household exposures: vulnerable persons (as defined above) who have had face-to-face exposure and/or shared confined air for > 1 hour.

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. Vaccination with Tdap vaccine is recommended for pregnant women with each pregnancy, optimally given between 27 and 32 weeks gestation, though beyond the one lifetime adult pertussis dose, further doses are not currently publicly funded. Please provide vaccine to all eligible persons who are not considered up-to-date.

Reporting

Report any suspected pertussis cases immediately to Public Health Sudbury & Districts for follow-up.

Should you have any questions, please contact the immunization program at 705.522.9200, ext. 301.

Sincerely,

Ariella Zbar, MD, CCFP, MPH, MBA, FRCPC
Associate Medical Officer of Health and Director, Clinical Services

---

Source

Ontario Agency for Health Protection and Promotion. Considerations for Public Health on Pertussis Case and Contact Management. September 2015.

This item was last modified on July 5, 2018