Quarterly Surveillance Report

Notifiable Sexually Transmissible Infections and Blood-borne Viruses in Western Australia

Period ending 30September2016

Vol. 13 (4), issued November2016

Contents

Summary

Chlamydia

Gonorrhoea

Infectious syphilis

HIV/AIDS

Hepatitis B

Hepatitis C

Notes:

  1. All data in this report are provisional and subject to future revision.
  2. To help place the data in this report in perspective, comparisons with other reporting periods are provided. As no formal statistical testing has been conducted, some caution should be taken with interpretation.
  3. Notifications for Christmas Island, Curtin, Leonora, Perth and Yongah Hill Immigration Detention Centres have been excluded from all analyses because of potential bias introduced through the inclusion of cases detected by screening of asylum seekers at these locations.

Copyright to this material is vested in the State of Western Australia unless otherwise indicated. Apart from any fair dealing for the purposes of private study, research, criticism or review, as permitted under the provisions of the Copyright Act 1968, no part may be reproduced or re-used for any purposes whatsoever without written permission of the State of Western Australia.

Produced by the Epidemiology & Surveillance Program,

Communicable Disease Control Directorate,

Department of Health, Western Australia.

Summary

Table 1 Number and percentage change of STI and BBV notifications by reporting period, WA

Notes:1 Historical five-year mean (i.e. from 2011 to 2015) for the current quarter.

2 Percentage change of the number of notifications in the current quarter compared to the historical five-year mean of the same quarter. Positive values indicate an increase in comparison to the historical five-year mean of the same quarter. Negative values indicate a decrease in comparison to the historical five-year mean of the same quarter.

3 Historical five-year mean (i.e. from 2011 to 2015) for the current 12-month period.

4 Percentage change of the number of notifications in the current 12-month period compared to the historical five-year mean for the same 12-month period. For interpretation of positive and negative values, see note 2.

Chlamydia

Figure 1 Number of chlamydia notifications in WA by month, for the two most recent 12-month periods

  • The number of chlamydia notifications for the 12-month period from October 2015toSeptember 2016was comparable to the previous 12-month period and the previous five-year mean, reflecting a trend for relative stability in chlamydia notifications over this period, after many years of increasing notifications (Table 1).

Table 2 Number and proportion of chlamydia notifications in WA by sex, for the two most recent 12-month periods

Notes:N/A = Not applicable

Table 3 Number and proportion of chlamydia notifications in WA by age group, for the two most recent 12-month periods

  • The age distribution of chlamydia notifications was similar to the previous 12-month period. The largest proportion of notifications was among 20 to 29 year olds (55%)and notifications among this age group remained relatively stable. The number of notifications among 25 to 34 year olds increased by 7%.

Table 4 Number and crude rate of chlamydia notifications in WA by Aboriginality, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

N/A = Not applicable

  • Thechlamydia notification rate increased by 13% among Aboriginal people and decreased by 3% among non-Aboriginal peopleresulting in an increase in the rate ratio compared to the previous 12-month period.

Table 5 Number and crude rate of chlamydia notifications in WA by region, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

Other = Interstate + Overseas residents diagnosed in WA

Unknown = Unknown residential address within WA

N/A = Not applicable

  • Chlamydia notification rates declined or remained stable in most regions exceptthe Goldfields and Midwest, where there were modest increases (26% and 29%, respectively).

Gonorrhoea

Figure 2 Number of gonorrhoea notificationsin WA by region and exposure category, for the two most recent 12-month periods

  • The total number of gonorrhoea notifications was 42% higher compared to the previous 12-month period and 53% higher than the previous five-year mean (Table 1).
  • In the Perth metropolitan area,the number of gonorrhoea notifications categorised as “heterosexual”(on the basis of enhanced surveillance data provided by notifying clinicians)increased by 33% in comparison to the previous 12-month period (n=1,259 vs. 773), and more than doubled in comparison to the previous five-year mean of 620 cases per year. The largest increases occurred among females, with a 74% increase compared to the previous 12-month period (n=607 vs. 348) and a 135% increase in comparison to the previous five-year mean of 258 cases per 12-month period.
  • The number of gonorrhoea notifications in the Perth metropolitan area categorised as “men who have sex with men” (MSM) increased by 23% in comparison to the previous 12-month period (n=491 vs. 400), and by72% in comparison to the previous five-year mean of 286 cases per 12-month period. The number of notifications peaked in the first quarter of 2016.

Table 6 Number and proportion of gonorrhoea notifications in WA by sex, for the two most recent 12-month periods

Notes:N/A = Not applicable

Table 7 Number and proportion of gonorrhoea notifications in WA by age group, for the two most recent 12-month periods

  • The age distribution of gonorrhoea notifications was similar to the previous 12-month period, with the number of notified cases increasing in all age-groups. The largest proportion of notifications was among 20 to 29 year olds (45%)and notifications among this age group increased by 42%.

Table 8 Number and crude rate of gonorrhoea notifications in WA by Aboriginality, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

N/A = Not applicable

  • The gonorrhoea notification rate increased by 22% among Aboriginal people andby 48% among non-Aboriginal people, resulting in a decreasein the rate ratio compared to the previous 12-month period.
  • Nonetheless, the rate of gonorrhoea among Aboriginal people was14-times higher than non-Aboriginal rates.
  • Aboriginal status was reported for 99.7% of notifications, reflective of the efforts of public health staff in ascertaining this information.

Table 9 Number and crude rate of gonorrhoea notifications in WA by region, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

Other = Interstate + Overseas residents diagnosed in WA

Unknown = Unknown residential address within WA

N/A = Not applicable

  • Trends in the gonorrhoea notification rate varied between regions. While the rate increased across most regions, the most notable was the almost three-fold increase in the Midwest region, with most of the increase among Aboriginal people. The rate in the Kimberley region remained stable.

Infectious syphilis

Figure 3 Number of infectious syphilis notifications in WA by region and exposure category, for the two most recent 12-monthperiods

  • The total number of infectious syphilis notifications wasmore than double the number in the previous 12-month period and almost three-timesthe previous five-year mean (Table 1).
  • In the Perth metropolitan area, the number of infectious syphiliscases categorised as MSM was more than double the previous 12-month period (n=196 vs. 76) and more than three-times the previous five-year mean of 59 cases per year. Notifications increased sharply in the first quarter of 2016 (n=60), and declined somewhat in the second quarter, and remain significantly elevated.
  • The number of infectious syphilis notifications attributed to heterosexual transmission in the Perth metropolitan areawas also more than double the previous 12-month period (n=37 vs. 16).

Table 10 Number and crude rate of infectious syphilis notifications by Aboriginality for the two most recent 12-month periods, WA

Notes:Rate = Crude notification rate per 100,000 population

N/A = Not applicable

  • The infectious syphilis notification rate increased by 10% among Aboriginal people (primarily associated with an ongoing outbreak in the Kimberley region)and more than doubled among non-Aboriginal people, resulting in a lower rate ratio compared to the previous 12-month period.

Table 11 Number and crude rate of infectious syphilis notifications by region for the two most recent 12-month periods, WA

Notes:Rate = Crude notification rate per 100,000 population

Other = Interstate + Overseas

Unknown = Unknown residential address within WA

N/A = Not applicable

  • While trends in infectious syphilis notifications varied between regions, most notable wasthe more than two-fold increase in the combined Perth metropolitan regions.While the notification rate remained highest in the Kimberley region, it remained stable in comparison to the previous 12-month period.
  • The high notification rate in the Kimberley region reflects the outbreak that commenced in northern Queensland in 2011 which spread to nearby areas in the Northern Territory in 2013, and thento the Kimberley region. A total of 76 infectious syphilis cases (49 female, 27 male) have been notified in the Kimberley region since the first case was identified in June 2014, with 15 cases notified in the third quarter of 2016. Prior to 2014, there had been no infectious syphilis notifications in the Kimberley region for two years.

HIV/AIDS

Figure 4 Number of HIV notifications in WA by quarter, for the two most recent 12-month periods

  • There were 117 new HIV notifications in the October 2015 to September 2016 period, a decrease compared to the previous 12-month period (n=130) (Table 1).
  • Following a decline in the number of HIV notifications to 20 cases in the April to June 2016 quarter, the number of cases increased to 34 in the July to September quarter (Figure 4).
  • Of the new HIV notifications in the October 2015 to September 2016 period, 102 (87%) were male and 15 (13%) were female. The male: female ratio for HIV notifications in this period was 6.8:1, which was double the ratio reported in the October 2014 to September 2015 (3.4:1).This was mainly due to a 48% decrease in the number of female HIV notifications (15 vs. 29 cases), while the number of males HIV notifications remained stable (102 vs. 100 cases).

Table 12 Number and proportion of HIV notifications in WA by age group, for the two most recent 12-month periods

  • The median age of newly notified HIV cases in the October 2015 to September 2016 period was 38 years (range: 16 to 73 years), similar to the median age reported for the previous 12-month period (37 years; range: 4 to 81 years). There were two notifications in the 0 to 16 age group, both of whom acquired HIV through vertical transmission overseas.

Table 13 Number and crude rate of HIV notifications in WA by Aboriginality, for the two most recent 12-month periods

Note:Rate = Crude notification rate per 100,000 population

  • In the most recent 12-month period there were four HIV notifications among Aboriginal people. The crude HIV notification rate for Aboriginal people is sensitive to small changes in the number of cases notified and decreased in the current period to be similar to the rate reported for non-Aboriginal people.

Table 14 Number and proportion of HIV notifications in WA by exposure, for the two most recent 12-month periods

  • In the current 12-month period there was a 7% decrease in the number of HIV notifications for which the exposure category was attributed to MSM. Most MSM notified with HIV in the current period reported acquiring their infection in Australia (70%).
  • The number of male cases attributed to heterosexual exposure in the current 12-month period was the same as the number reported for the previous period. The majority of these cases in the current period were men who acquired HIV overseas (70%).
  • There was a 48% decrease in the number of female notifications attributed to heterosexual exposures in the current period. Most of these women were born overseas and had acquired HIV overseas (69%).

Hepatitis B

Figure 5 Number of hepatitis B notifications in WA by disease status, for the two most recent 12-month periods

Table 15 Number of newly acquired and unspecified hepatitis B notifications in WA, for the two most recent 12-month periods

  • The number of newly acquired hepatitis B notifications remained stable and the number of unspecified hepatitis B notifications increased by 16%, compared to the previous 12-month period. Thesharp increase in unspecified hepatitis B notifications in May and June 2016 is a reporting artefact resulting from the addition of a backlog of notifications from one pathology laboratory.

Table 16 Number and proportion of hepatitis B notifications (newly acquired + unspecified) in WA by sex, for the two most recent 12-month periods

Note:N/A = Not applicable

Table 17 Number and proportion of hepatitis B notifications (newly acquired + unspecified) in WA by age group, for the two most recent 12-month periods

  • There was little change in the age distribution of hepatitis B cases in the past two 12-month periods.

Table 18 Number and crude rate of hepatitis B notifications (newly acquired + unspecified) in WA by Aboriginality, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

N/A = Not applicable

Table 19 Number and crude rate of hepatitis B notifications (newly acquired + unspecified) in WA by region, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

Other = Interstate + Overseas

Unknown = Unknown residential address within WA

N/A = Not applicable

  • Trends in the total hepatitis B notification rate varied between regions. Although based on small numbers, the rate decreased in the Midwest region and increased in the Kimberley region.

Hepatitis C

Figure 6 Number of hepatitis C notifications in WA by disease status, for the two most recent 12-month periods

Table 20 Number of hepatitis C notifications in WA by disease status, for the two most recent 12-month periods

Table 21 Number, proportion and ratio of hepatitis C notifications (newly acquired + unspecified) in WA by sex, for the two most recent 12-month periods

Note:N/A = Not applicable

Table 22 Number and proportion of hepatitis C notifications (newly acquired + unspecified) in WA by age group, for the two most recent 12-month periods

  • There was little change in the age distribution of total hepatitis C notifications between the two 12-month periods.

Table 23 Number and crude rate of hepatitis C notifications (newly acquired + unspecified) in WA by Aboriginality, for the two most recent 12-month periods

Notes: Rate = Crude notification rate per 100,000 population

N/A = Not applicable

Table 24 Number and crude rate of hepatitis C notifications (newly acquired + unspecified) in WA by region, for the two most recent 12-month periods

Notes:Rate = Crude notification rate per 100,000 population

Other = Interstate + Overseas

Unknown = Unknown residential address within WA

N/A = Not applicable

  • Trends in the notification rate varied between regions. Although based on small numbers, the rate decreased in the Kimberley region and increased in the Midwest region.

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© Department of Health 2016