Pertussis on the Rise in 2005

The Public Health Unit has been receiving a greatly increased number of pertussis notifications in recent months. The number of notifications in south-eastern Sydney residents received this year up to 30 June has been 310, almost double the number for the same period in 2004.

The table below shows the distribution of the cases and average monthly notification rates for residents within the boundaries of each Division of General Practice.

Table 1. Number of cases and monthly notification rates for Pertussis, by General Practice Division of residence in South Eastern Sydney, January-June 2005
 

	Number of Cases, January to June 2005		Average monthly rate of Pertussis (per 100,000 popn)
	2004	2005	2004	2005
Eastern Sydney Division	29	73	3.48	8.77
South Eastern Sydney Division	75	109	5.73	8.33
St.George Division	34	56	2.7	4.45
Sutherland Division	44	72	3.61	5.91
Overall	182	310	3.94	6.71

The Public Health Unit has followed several clusters of pertussis in maternity units during this period. In these clusters, the cases comprised healthcare workers as well as newborns and mothers. We have also been involved in the follow up of pertussis in GPs who may have placed their patients and fellow staff at risk.

Healthcare workers, including GPs, should absent themselves from work whilst infectious with pertussis (and any other significant communicable disease).

The majority of cases are in adults (see Graph below), so we would like to take this opportunity to remind you of the recommendations in the current Australian immunisation handbook (p. 211) for the use of booster diptheria-tetanus-pertussis vaccine (dTpa; brand name Boostrix)

• Before planning pregnancy, or for both parents as soon as possible after delivery of an infant
• For adults working with young children; especially for childcare workers and health-care workers such as GPs, and maternity and newborn nursery staff
• Adolescents at 15-17 years (NB: a publicly funded dTpa vaccination program is currently being run in high schools for year 7 students)
• Any adult expressing an interest in receiving a booster dose of dTpa, given that a primary course (3 doses) of DTP has been completed in the past; it may also be given at 50 years of age in place of ADT.

Pertussis is transmitted by droplet infection and direct contact with respiratory secretions of infected persons. The spread of pertussis can be controlled in individual cases by administration of erythromycin:

• To infectious cases (ie. those within 3 weeks of ONSET of cough)
• As prophylaxis to high-risk contacts (such as all members of a household containing an infant under 12 months of age).

Medical practitioners and hospital managers (or a delegated clinician) are required to notify the details of every pertussis case on clinical suspicion. This should be followed by confirmatory tests. Within 2-3 weeks of onset of symptoms, the appropriate tests are culture or PCR on a pernasal swab. After this time, the most appropriate test is Bordetella IgA serology (although the IgA response is not reliable in young children). Pre-vaccination screening for immunity is not recommended for pertussis because there is no validated screening test. (NB: natural pertussis infection may not confer long-term immunity).

To discuss pertussis notification, laboratory testing, contact tracing and prophylaxis, or to ask about any aspect of case management, please do not hesitate to phone the Public Health Unit’s Infectious Diseases Team on 9382 8333.