PERTUSSIS REPORT. November 2013

Transcription

1 PERTUSSIS REPORT Data contained within this monthly report is based on information recorded on EpiSurv by public health service staff as at 12 December 213. Changes made to EpiSurv data after this date will not be reflected in this report. The results presented may be further updated and should be regarded as provisional. Summary In, 214 cases of pertussis were notified, including 94 confirmed, 95 probable, 9 suspect, and 16 cases still under investigation. The number of cases in November has decreased compared to the previous month (243 cases). Eighteen (8.4%) of the notified cases were aged less than 1 year. Twenty cases were hospitalised and no deaths were reported. Although weekly numbers had been trending downward since week 8 they have more or less been stable since week 16. Weekly notifications during November remain considerably lower than last year (Figure 1). In, the highest number of cases (excluding cases under investigation) were reported by Counties Manukau (39 cases), Canterbury (38 cases), and Nelson Marlborough (26 cases) DHBs. The overall rate in November was 4.5 per population (198 cases). The DHB with the highest rate was West Coast (21.3 per, 7 cases), followed by Nelson Marlborough (18.5 per, 26 cases), and Hutt Valley (9.7 per, 14 cases) DHBs. Since 1 January 213, 339 cases of pertussis have been notified, including 1518 confirmed, 167 probable, 135 suspect, and 67 cases still under investigation. Two hundred and fifty (7.4%) of the notified cases were aged less than 1 year. Two hundred and eleven cases were hospitalised and two deaths were reported. Since 1 January 213, high numbers of cumulative cases (excluding cases still under investigation) have been reported by Canterbury (548 cases), Nelson Marlborough (419 cases), and Waikato (284 cases) DHBs. The overall cumulative rate was 75. per (3323 cases). The DHB with the highest cumulative rate was Nelson Marlborough (297.8 per, 419 cases), followed by West Coast (182.4 per, 6 cases), and Canterbury (19.5 per, 548 cases) DHBs. This report summarises pertussis notifications for 213 (cumulative and a monthly summary). It incorporates the temporal distribution of cases, the distribution of cases by age, ethnicity (prioritised), and DHB, as well as hospitalisations and immunisation status. The case classification used in this report is specified on the last page. Case definitions have changed following the release of the Ministry of Health s Communicable Disease Control Manual 212 on 31 May 212. ESR Pertussis Report Page 1

2 Trends in pertussis notifications Figure 1: Number of pertussis notifications by week reported, Number of pertussis notifications Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Surveillance week (Month) Note: Includes confirmed, probable, suspect cases and notifications still under investigation. Figure 2: Number of pertussis notifications and hospitalisations by calendar month-year, 1998 to 3 7 Hospitalised Total notifications <1 year 5 Number of pertussis notifications Number of hospitalisations Month (Year) Note: Includes confirmed, probable, suspect cases and notifications still under investigation. ESR Pertussis Report Page 2

3 In the following pages, all analyses include confirmed, probable and suspect cases only. Notifications that are still under investigation are excluded. Figure 3: Comparative trend of the number of pertussis notifications by week reported, Number of pertussis notifications (excluding under investigation) Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Note: Includes confirmed, probable and suspect cases only. Surveillance week (Month) Age Table 1: Number of pertussis notifications and rate (cases per population) by age group, 213 Cumulative 1 notifications Age group (Years) All cases Rate 2 Hospitalisations New cases Hospitalisations < Overall Cumulative notifications since 1 January 213, includes confirmed, probable and suspect cases only. 2 Rate of pertussis cases per population calculated using 212 mid-year population estimates. ESR Pertussis Report Page 3

4 Figure 4: Pertussis rate (cases per population) by age group and ethnicity, 213 Pertussis rate (cases per population) Māori Asian * * Pacific Peoples MELAA. < Age group (Years) Note: Cumulative notifications since 1 January 213, includes confirmed, probable and suspect cases only. Denominator data used to determine rates are based on the proportion of people in each ethnic group from the estimated resident 6 census population applied to the 212 mid-year population estimates from Statistics New Zealand. * Rate based on fewer than five cases. Ethnicity Table 2: Number of pertussis notifications and rate (cases per population) by ethnicity (prioritised), 213 Cumulative 1 notifications Ethnicity All cases (Rate 2 ) Hosp 3 (% 4 ) <1 year 5 (Rate 2 ) New cases Hosp 3 <1 year 5 Māori 454 (7.1) (496.) Pacific Peoples 211 (79.1) (864.2) Asian 15 (25.7) (171.) MELAA 15 (39.7) 1 - European or Other 2389 (77.7) (38.6) Unknown Overall 3323 (75.) (41.1) Cumulative notifications since 1 January 213, includes confirmed, probable and suspect cases only. 2 Rate of pertussis cases per population. Denominator data used to determine rates are based on the proportion of people in each ethnic group from the estimated resident 6 census population applied to the 212 mid-year population estimates from Statistics New Zealand. Where fewer than five cases have been notified a rate has not been calculated. 3 Number of hospitalised notifications. 4 Percentage of hospitalised notifications. 5 Number of notifications in the <1 year age group. ESR Pertussis Report Page 4

5 District health board Figure 5: Pertussis rate (cases per population) by district health board, 213 District health board Nelson Marlborough West Coast Canterbury Tairawhiti Wairarapa Northland Southern Waikato South Canterbury Whanganui Capital and Coast Hutt Valley MidCentral Taranaki Bay of Plenty Counties Manukau Auckland Waitemata Lakes Hawke's Bay Pertussis rate (cases per population) Note: Cumulative notifications since 1 January 213, includes confirmed, probable and suspect cases only. Rate of pertussis cases per population calculated using 212 mid-year population estimates. Immunisation status of confirmed notifications Table 3: Immunisation status of confirmed pertussis notifications, Age group Total cases One dose Two Three Four Five Vaccinated (no dose info) Not vaccinated Unknown <6wks wks 2mths mths 2 2 5mths 3yrs yrs yrs Total Note: Immunisation status has been extracted from EpiSurv. Health professionals may use a range of sources to update immunisation status including the National Immunisation Register, parental recall and Well Child book records. 1 Children aged <6 weeks are not eligible for immunisation. ESR Pertussis Report Page 5

6 Table 4: Immunisation status of confirmed pertussis notifications, 213 Age group Total cases One dose Two Three Four Five Vaccinated (no dose info) Not vaccinated Unknown <6wks wks 2mths mths mths 3yrs yrs yrs Total Note: Immunisation status has been extracted from EpiSurv. Health professionals may use a range of sources to update immunisation status including the National Immunisation Register, parental recall and Well Child book records. 1 Children aged <6 weeks are not eligible for immunisation. ESR Pertussis Report Page 6

7 Appendix Table 5: Number of pertussis notifications and rate (cases per population) by district health board, 213 Cumulative 1 notifications District health board All cases Rate 2 Hosp 3 <1 year 4 New cases Hosp 3 <1 year 4 Northland Waitemata Auckland Counties Manukau Waikato Lakes Bay of Plenty Tairawhiti Taranaki Hawke's Bay Whanganui MidCentral Hutt Valley Capital and Coast Wairarapa Nelson Marlborough West Coast Canterbury South Canterbury Southern Total Cumulative notifications since 1 January 213, includes confirmed, probable and suspect cases only. 2 Rate of pertussis cases per population calculated using 212 mid-year population estimates. 3 Number of hospitalised notifications. 4 Number of cases in the <1 year age group. ESR Pertussis Report Page 7

8 Figure 6: Pertussis rate (cases per population) by age group (<1 year vs. 1+ years), <1 year 1+ years Pertussis rate (cases per population) Year Note: Includes confirmed, probable and suspect cases only. Rate of pertussis cases per population calculated using mid-year population estimates. Figure 7: Trends in pertussis rates (cases per population) by age group and ethnicity, <1 year 5 14 years Māori Pacific Peoples Māori Pacific Peoples Pertussis rate (cases per population) Asian/MELAA European or Other Asian/MELAA European or Other years 15+ years Pertussis rate (cases per population) Māori Pacific Peoples Asian/MELAA European or Other Year Māori Asian/MELAA Pacific Peoples European or Other Year Note: Includes confirmed, probable and suspect cases only. Rate of pertussis cases per population calculated using mid-year population estimates. ESR Pertussis Report Page 8

9 Figure 8: Monthly pertussis rate (cases per population) by district health board, since January 212 Note: Includes confirmed, probable and suspect cases only. Figure 9: Monthly pertussis cases by district health board, since January 212 Note: Includes confirmed, probable and suspect cases only. ESR Pertussis Report Page 9

10 Case classification for pertussis notification in New Zealand up to 3 May 212 Confirmed A clinically compatible illness that is laboratory confirmed by isolation of Bordetella pertussis from a pernasal swab, or epidemiologically linked to a confirmed case. Probable Cough lasting longer than two weeks and one or more of the following: Paroxysmal cough Cough ending in vomiting or apnoea Inspiratory whoop for which there is no other known cause. Suspect In children under five years of age, any paroxysmal cough with whoop, vomiting or apnoea for which there is no other known cause. Other Status recorded as under investigation or suspect case. Notifications Include confirmed cases, probable, and other as specified above. Case classification for pertussis notification in New Zealand from 31 May 212 Confirmed A clinically compatible illness that is laboratory confirmed by isolation of B. pertussis or detection of B. pertussis nucleic acid, preferably from a nasopharyngeal swab, or is epidemiologically linked to a confirmed case. Probable A clinically compatible illness with a high B. pertussis IgA test or a significant increase in antibody levels between paired sera at the same laboratory OR A cough lasting longer than two weeks and with one or more of the following, for which there is no other known cause: Paroxysmal cough Cough ending in vomiting or apnoea Inspiratory whoop Suspect In children under five years of age any paroxysmal cough with whoop, vomiting or apnoea for which there is no other known cause. Under A case that has been notified, but information is not yet available to classify it as suspect, investigation probable or confirmed. Notifications Include confirmed cases, probable, suspect and under investigation as specified above. This report is available at: ESR Pertussis Report Page 1