Enhanced Surveillance for Pertussis (whooping cough)

Advisory Alert

May 22, 2019

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To community health care providers:

Re: Enhanced Surveillance for Pertussis (whooping cough)

I am writing to advise you that there has been recent pertussis activity occurring locally. Pertussis is cyclical in nature, with peaks in incidence occurring every two to five years. The last local peak in pertussis activity was from July 2015 to August 2016, with 27 confirmed cases. Since then, disease activity has been sporadic. Please consider pertussis in the differential diagnosis of patients presenting to you with signs and symptoms outlined 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 younger than four 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 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.

The clinical course is divided into three stages:

1. Catarrhal stage: characterized by mild upper respiratory tract symptoms with a mild occasional cough that lasts one to two weeks then progresses to the next stage.
2. Paroxysmal stage: presents with an increase in the severity and frequency of the cough and lasts one to two months, sometimes longer. Paroxysms are characterized by repeated violent coughs. 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 eventually disappears.

Pertussis is highly communicable during the catarrhal stage and during the first two weeks of the paroxysmal stage. Communicability gradually decreases and becomes negligible after three weeks. Protection against infection is not lifelong and wanes after natural infection and vaccination.

Laboratory Testing

Laboratory testing via nasopharyngeal swab should only be done on patients with clinical signs and symptoms. Order the Bordetella pertussis kit through the Public Health Ontario Laboratory. Follow the instructions in the kit.

Testing asymptomatic persons who are household contacts of a case should be avoided as the PCR assay is very sensitive and will detect even low levels of DNA (e.g., even non-viable bacteria located in the nasopharynx). Also, testing should not be used to guide whether to offer post-exposure prophylaxis.

Optimal timing for PCR testing for pertussis is within three weeks of cough onset, when bacterial DNA are 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

Chemoprophylaxis should only be provided to high risk contacts as soon as possible after exposure. It is unlikely beneficial after 21 days following initial contact.

High risk contacts include:

• Household contacts (including attendees at home day care) where there is a vulnerable person defined as an infant less than one 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 air in a confined space for more than one hour.

Vaccination Considerations

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 are 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. Please note that additional doses for adults beyond the one lifetime adult dose are not publicly-funded. Please provide the vaccine to all eligible persons who are not considered up-to-date.

Reporting

Immediately report any suspected and confirmed pertussis cases to Public Health Sudbury & Districts for follow-up.

This includes cases and contacts of pertussis where treatment or chemoprophylaxis have been provided.

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

 

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This item was last modified on May 22, 2019