Northern Territory Sexual Health and Blood Borne Viruses Unit
Surveillance Update
Vol. 12 No. 2,
Jul-Sep 2011 & Oct-Dec 2011
A. Introduction
The Sexual Health and Blood Borne Virus Unit regularly produces the Surveillance Update to present quarterly statistics for notifiable sexually transmissible infections (STIs) and blood borne viruses (BBVs) in the Northern Territory (NT). It is part of the NT’s effort in continuous monitoring of the epidemiology of STIs and BBVs. It is hoped that health service providers may utilise the information provided in this report in the planning of targeted prevention and intervention programs to address the STI/BBV issues in the NT.
The statistics reported in this issue are for July-December 2011, and where possible, the annual statistics for 2011 are also presented. The notification data were extracted from the NT Notifiable Diseases System (NTNDS) of the Centre for Disease Control (CDC) on 16 Feb 2012. Additional data for notifications of HIV were retrieved from the HIV database maintained by the Sexual Health and Blood Borne Virus Unit (SHBBVU) on the same day. The statistics of Australia and other States/Territories used for comparison were extracted from the National Notifiable Disease System and the ‘HIV/AIDS, Viral Hepatitis and Sexually Transmissible Infections in Australia Annual Surveillance Report 2011’ published by the Kirby Institute. The population data for the NT were provided by the Health Gains Planning. As the NT population data for 2011 are not available yet, data for 2010 were used to calculate 2011 rates.
All notification rates for quarters and six-month periods presented in this report are crude annualised rates without standardisation. Due to a proportion of notifications being categorised as ‘interstate’, the sum of district-specific notifications presented in tables with district breakdown may be lower than the total number of notifications shown in other tables. When calculating Aboriginal and non-Aboriginal notification rates, adjustments were made so that the notifications for which ethnicity are not known were allocated to the two categories proportional to their known distribution in the two populations. These rates are named adjusted rates in this report.
A considerable body of literature has shown that, for common STIs such as gonorrhoea and chlamydia, notification rates and testing rates are often highly correlated. In other words, the numbers of STI notifications are often subject to variations in the amount of testing performed. This is particularly true for the NT where the prevalence of STIs is known to be high, opportunistic screening tests have been recommended for and frequently performed in young people, and large-scale community-wide STI screens are not uncommon, all of which can lead to an increase in notifications. Readers are advised to take this factor into consideration when interpreting the notification statistics in this surveillance update.
B. Quarterly Statistics
Table B.1.1 Quarterly numbers and rates (per 100,000) of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis notifications, NT, Jul-Dec 2011
Gonorrhoea Chlamydia
Infectious
Syphilis Trichomoniasis Quarter
Cases Rate Cases Rate Case Rate Case Rate 2011
Jul-Sep 473 823.8 713 1241.8 6 10.4 789 1374.1 Oct-Dec 500 870.8 655 1140.7 3 5.2 778 1355.0 Jul-Dec
total 973 847.3 1368 1191.2 9 7.8 1567 1364.5 2011 total 2029 883.4 2710 1179.9 32 13.9 2905 1264.8 2010
Jul-Sep 565 984.0 785 1367.1 8 13.9 723 1259.2 Oct-Dec 497 865.6 630 1097.2 11 19.2 614 1069.3 Jul-Dec
total 1062 924.8 1415 1232.2 19 16.5 1337 1164.3 2010 total 1971 858.2 2692 1172.1 45 19.6 2398 1044.1
Figure B.1.1 Notification rates of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis, NT, 2007-2011
0 200 400 600 800 1000 1200 1400
Gonorrhoea Chlamydia Infectious Syphilis
Trichomoniasis
Disease
Notification rate (per 100,000 population)
2007 2008 2009 2010 2011
Table B.1.2 Quarterly numbers and rates (per 100,000) of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis by gender, NT, Jul-Dec 2011
Gonorrhoea* Chlamydia
Infectious
Syphilis Trichomoniasis Gender
Cases Rate Cases Rate Cases Rate Cases Rate Males
Jul-Sep 215 722.4 302 1014.7 4 13.4 142 477.1
Oct-Dec 216 725.7 274 920.6 2 6.7 118 396.5
Total 431 724.1 576 967.6 6 10.1 260 436.8
Females
Jul-Sep 258 932.9 411 1486.1 2 7.2 647 2339.5
Oct-Dec 284 1026.9 381 1377.7 1 3.6 660 2386.5
Total 542 979.9 792 1431.9 3 5.4 1307 2363.0 2011 total
Males 926 777.8 1,090 915.6 16 13.4 438 367.9
Females 1102 996.2 1,620 1464.4 16 14.5 2467 2230.1 Total 2028 883.0 2,710 1179.9 32 13.9 2905 1264.8
* One case with missing data on sex.
Figure B.1.2 Notification rates of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis by gender, NT, 2007-2011
0 400 800 1200 1600 2000 2400
2007 2008 2009 2010 2011 2007 2008 2009 2010 2011 Male Female
Notification Rate (per 100,000 population)
Gonorrhoea Chlamydia Infectious Syphilis Trichomoniasis
Table B.1.3 Quarterly numbers and rates (per 100,000) of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis notifications by ethnicity, NT, Jul-Dec 2011
Ethnicity Gonorrhoea Chlamydia
Infectious
Syphilis Trichomoniasis Quarter Cases Rate Cases Rate Cases Rate Cases Rate Aboriginal
Jul-Sep 435 2518.7 402 2327.7 5 29.0 766 4435.3 Oct-Dec 461 2669.3 374 2165.5 3 17.4 746 4319.5 Total 896 2594.0 776 2246.6 8 23.2 1512 4377.4
Non-Aboriginal
Jul-Sep 31 77.2 267 665.0 1 2.5 20 49.8
Oct-Dec 33 82.2 236 587.8 0 0.0 23 57.3
Total 64 79.7 503 626.4 1 1.2 43 53.6
Unknown
Jul-Sep 7 44 0 3
Oct-Dec 6 45 0 9
Total 13 89 0 12
2011 Total (Adjusted)
Aboriginal 1902 2753.0 1712 2478.1 28 40.5 2824 4087.8
Non-Aboriginal 127 79.2 998 621.5 4 2.5 81 50.5
Figure B.1.3 Adjusted notification rates of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis by ethnicity, NT, 2011
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Gonorrhoea Chlamydia Infectious Syphilis
Trichomoniasis
Notification rate (per 100000 population)
Aboriginal Non-Aboriginal
Table B.1.4 Quarterly numbers and rates (per 100,000) of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis notifications by district, NT, Jul-Dec 2011
Gonorrhoea Chlamydia
Infectious
Syphilis* Trichomoniasis District Cases Rate Cases Rate Cases Rate Cases Rate Darwin
Jul-Sep 85 237.2 344 960.0 1 2.8 198 552.5
Oct-Dec 89 248.4 299 834.4 1 2.8 199 555.3
Total 174 242.8 643 897.2 2 2.8 397 553.9
Katherine
Jul-Sep 96 1920.0 91 1820.0 1 20.0 161 3220.0
Oct-Dec 91 1820.0 82 1640.0 2 40.0 157 3140.0
Total 187 1870.0 173 1730.0 3 30.0 318 3180.0 East Arnhem
Jul-Sep 33 782.1 57 1350.9 0 0.0 137 3246.8
Oct-Dec 27 639.9 44 1042.8 0 0.0 101 2393.6
Total 60 711.0 101 1196.8 0 0.0 238 2820.2
Barkly
Jul-Sep 23 1388.5 19 1147.0 2 120.7 43 2595.8
Oct-Dec 17 1026.3 9 543.3 0 0.0 48 2897.7
Total 40 1207.4 28 845.2 2 60.4 91 2746.8
Alice Springs
Jul-Sep 224 2091.9 188 1755.7 1 9.3 238 2222.7
Oct-Dec 266 2484.2 206 1923.8 0 0.0 252 2353.4
Total 490 2288.1 394 1839.8 1 4.7 490 2288.1
* One syphilis notification from interstate was not included.
Figure B.1.4 Notification rates of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis by district, NT, 2011
0 500 1000 1500 2000 2500 3000 3500
Gonorrhoea Chlamydia Infectious Syphilis Trichomoniasis
Notification rate (per 100,000 population)
Darwin Katherine East Arnhem Barkly Alice Springs
Table B.1.5 Number and rate (per 100,000) of gonorrhoea, chlamydia, infectious syphilis and trichomoniasis notifications by 5-year age group, Jul-Dec 2011
Gonorrhoea Chlamydia
Infectious
Syphilis Trichomoniasis Age
group Cases Rate Cases Rate Cases Rate Cases Rate
<10 2 11.0 2 11.0 0 0.0 1 5.5
10-14 46 548.9 44 525.0 1 11.9 41 489.2
15-19 285 3384.0 380 4512.0 3 35.6 261 3099.0
20-24 251 2648.8 434 4580.0 0 0.0 287 3028.7
25-29 166 1571.8 262 2480.8 1 9.5 246 2329.3
30-34 115 1218.0 90 953.2 2 21.2 196 2075.8
35-39 48 516.7 60 645.9 0 0.0 183 1970.0
40-44 28 329.4 42 494.0 1 11.8 157 1846.7
45-49 17 210.7 17 210.7 1 12.4 99 1227.3
50-54 6 82.5 23 316.1 0 0.0 40 549.7
55-59 3 48.3 10 161.0 0 0.0 31 499.1
60-64 1 21.3 2 42.6 0 0.0 13 277.2
65+ 5 78.6 1 15.7 0 0.0 12 188.6
Unknown 0 1 0 0
Total 973 847.3 1368 1191.2 9 7.8 1567 1364.5
Figure B.1.5 Notification rate of gonorrhoea, chlamydia, syphilis and trichomoniasis notifications by 5-year age group, 2011
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
<10 10- 14
15- 19
20- 24
25- 29
30- 34
35- 39
40- 44
45- 49
50- 54
55- 59
60- 64
65+
Age group
Notification rate (per 100,000 population) Gonorrhoea Chlamydia Trichomoniasis Infectious Syphilis
B.1 Gonorrhoea
A total of 973 cases of gonorrhoea were notified in this reporting period, giving a notification rate of 847.3 per 100,000 (Table B.1.1). Both the number and the rate of notifications for 2011 were close to those for 2010. The rates for these two most recent years were considerably higher than the rates for the previous three years (more than 20% higher), and represented a reverse of the previously existing decreasing trend.
As was the case in previous years, the rate for females was considerably higher than the male rate both in this reporting period and in 2011 (annual rate ratio 1.3:1, see Table B.1.2). The annual rate for females increased by approximately 10% between 2010 and 2011. In contrast, there was a slight decrease in the male rate during the same time (approximately 4%, see Fig. B.1.2).
The Aboriginal to non-Aboriginal rate ratio for this reporting period was about 33 to 1 (Table B.1.3); after adjusting for notifications with unknown ethnicity, about 93.7% of all notifications in 2011 were Aboriginal – both figures were close to the figures reported for 2010. At the district level, Alice Springs continued to record the highest rate of notification, followed by Katherine (Table B.1.4).
The highest age-specific rates in this reporting period were recorded in the 15-19 and 20-24 year age groups, which accounted for 55.1% of all notifications. (Table B.1.5 and Figure B.1.5). Two cases were recorded in the age group of under 10 years and 46 in the 10-14 year age group.
B.2 Genital Chlamydia
A total of 1,368 cases were notified in this reporting period, compared with 1415 cases in the same period in 2010 (Figure B.1.1 and Table B.1.1). The annual notification rate for 2011 remained at the same high level as that for 2010. Like the rates for gonorrhoea, the chlamydia rates for these two most recent years were considerably higher than the rates for the three previous years (more than 20%
higher).
The difference in notification rates of chlamydia between females and males was greater than that for gonorrhoea rates; the annual rate for females for 2011 was 60%
higher than the male rate. (it was 28% for gonorrhoea; see Table B.1.2). The annual rate for 2011 had remained at about the same level as that for 2010 in both sexes (Figure B.1.2).
About 57% of notifications in this reporting period were Aboriginal cases, and the Aboriginal rate was 3.6 times the non-Aboriginal rate (Table B.1.3). The proportion of notifications with unknown status for ethnicity remained at the level of 6.5%,
comparing with the corresponding proportion for gonorrhoea notifications at 1.5%.
Darwin recorded the highest number of notifications among all districts, followed by Alice Springs (Table B.1.4). However, the highest notification rate was recorded in Alice Springs. The rate for Alice Springs for this six-month period decreased by nearly 20% when compared with the corresponding rate for 2010 (2260.0 per 100,000).
The 15-19 and 20-24 year age groups continued to record the highest age-specific rates (Table B.1.5). These two age groups accounted for about 60% of all
notifications. Two cases notified in this reporting period were under 10 years of age and 44 in the 1—14 year age group.
B.3 Infectious Syphilis
Only 9 cases of infectious syphilis were notified in this six-month period, compared with 19 cases in the same period in 2010 (Table B.1.1 and Figure B.1.1). In 2011, the total number of notifications was 32 (45 in 2010), giving an annual notification rate of 13.9 per 100,000, which represents a nearly 30% decrease when compared with the 2010 rate (19.6 per 100,000). However, this rate was still more than two times higher than the notification rate for Australia (5.5 per 100,000 in 2011).
As usual, there were more male notifications than female ones (male to female rate ratio was almost 2:1, see Table B.1.2). Eight out of the nine cases notified in this period were Aboriginal (88.9%, Table B.1.3). The Aboriginal to non-Aboriginal rate ratio (using adjusted annual rates) was 16:1, significantly lower than those reported in previous years.
Katherine and Barkly districts continued to record relatively higher numbers of notifications compared with those for Darwin and Alice Springs (Table B.1.4). The only district that recorded more than 10 notifications in 2011 was Barkly (11 cases).
The majority of these Barkly notifications were diagnosed in a local outbreak. In terms of age-specific rates, the highest was recorded in the 15-19 year age group.
As shown in Figure B.3.1, the rate of notification has generally been on the decrease in both categories since 2007.
Figure B.3.1 Rate of syphilis notifications by category, NT, 2007-2011
0 20 40 60 80 100
2007 2008 2009 2010 2011
Year
Notification rate per 100000 population
Less than 2 years duration Greater than 2 yrs or unknown duration
There was no congenital syphilis notification in 2011.
B.4 Trichomoniasis
Compared with the same period in 2010, the number of notifications of
trichomoniasis in this reporting period increased by 17.2% (Table B.1.1 and Figure
B.1.1). In 2011, trichomoniasis replaced chlamydia for the first time as the most frequently notified disease in the NT. The annual number and rate of notification both increased by a significant 21.1% compared with the number and rate for 2010.
The majority of notifications (83.4%) were recorded in females (Table B.1.2). An even higher proportion (96.5%) of notifications was recorded in the Aboriginal population (Table B.1.3). The adjusted Aboriginal to non-Aboriginal rate ratio for 2011 was about 81 to 1. The highest rate was recorded in Katherine, followed by East Arnhem (Table B.1.4).
As was the case with gonorrhoea and chlamydia, the highest rates were recorded in the 15-19 and 20-24 year age groups, in which approximately 35% of all notifications were recorded (Table B.1.5). One case was recorded in the age group of under 10 years and 41 in the 10-14 year age group.
The sharp increase in trichomoniasis notification in 2011 is of concern. We examined the laboratory testing data (which contain all test results) supplied by the only
pathology laboratory offering nucleic acid test to remote districts in the NT (where the vast majority of notifications were recorded), and found that the number of tests in 2011 increased by 30% over the number of tests in 2010 (Figure B.4.1). However, the annual positivity rate (the proportion of tests showing positive results) remained at approximately the same level during 2008-2011. The increase in case-detection due to increased testing had accounted for the majority of the increase in notification.
This plus the fact that the positivity rate remained at about the same level at least indicate that there was no evidence that the prevalence among those tested in 2011 increased.
Figure B.4.1 Testing statistics of trichomoniasis by nucleic acid testing based on testing data supplied by a major pathology laboratory, NT, 2005-2011
Trichomonas testing statistics by nucleic acid testing, NT
0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000
2005 2006 2007 2008 2009 2010 2011
Number of tests performed
0%
5%
10%
15%
20%
25%
Positivity rate
Number of tests Positivity rate
B.5 Donovanosis
There were no donovanosis notifications recorded in 2010.
B.6 Other Sexually Transmitted Infections
There were no notifications of chancroid or lymphogranuloma venereum recorded in 2010.
B.7 Hepatitis C
In this reporting period, 110 cases were notified, 76 (69.1%) of them males and 33 (30.0%) females (there was one notification whose sex was unknown; see Table B.7.1). The total number of cases in 2011 was close to that of 2010 (Fig. B.7.1).
Actually, the annual number of notifications had remained at approximately the same level in the last five years (though it was slightly lower in 2009).
Two cases (1 male and 1 female) were classified as ‘newly acquired’, and all the rest were ‘unspecified’ (98.2%, see Table B.7.2). Non-Aboriginal cases accounted for 68.2% of all, and the ethnicity was unknown in 8.2% of notifications. The notification rate for males was about 2.1 times the female rate. The non-Aboriginal rate was about 1.2 times the Aboriginal rate, which represented a much smaller difference between the two sub-populations compared to the same statistic for the same period of 2010 (2.3 to 1).
Figure B.7.1 Number of hepatitis C notifications by sex, NT, 2007-2011
0 50 100 150 200 250
2007 2008 2009 2010 2011
Number of notifications
Female Male Total
Table B.7.1 Number and rate of hepatitis C by sex and ethnicity, NT, Jul-Dec 2011 Quarter Sex Aboriginal Non-Aboriginal Unknown Total
Case Rate Case Rate Case Case Rate
Jul-Sep Female 5 56.9 6 31.8 1 12 43.4
Male 8 94.3 23 108.1 4 35 117.6
Unknown 0 0 1 1
Total 13 75.3 29 72.2 5 48 83.6
Oct-Dec Female 4 45.5 17 90.1 0 21 75.9
Male 9 106.1 29 136.3 3 41 137.8
Total 13 75.3 46 114.6 3 62 108.0
Jul-Dec Female 9 51.2 23 60.9 1 33 59.7
Male 17 100.2 52 122.2 7 76 127.7
Unknown 0 0 1 1
Total 26 75.3 75 93.4 8 110 95.8
Table B.7.2 Number of hepatitis C notifications by sex, ethnicity and disease categories, NT, Jul-Dec 2011
Type Gender Indigenous status
Aboriginal
Non-
Aboriginal Unknown
Total %
Female 0 1 0 1
Newly
acquired Male 0 1 0 1
1.8%
Female 9 22 1 32
Male 17 51 7 75
Unspecified Unknown 0 0 1 1
98.2%
Total 26 75 9 110
% 23.6% 68.2% 8.2%
Table B.7.3 Number and annualised rate of hepatitis C notifications by gender and district, NT, Jul-Dec 2011
Case Rate Case Rate Case Rate Case Rate Case Rate
Jul-Sep Female 10 59.1 0 0.0 0 0.0 0 0 2 36.9
Male 28 148.1 0 0.0 1 46.0 1 116.9 4 75.7
Unknown 1 0 0 0 0
Oct-Dec Female 17 100.4 0 0.0 1 48.9 0 0.0 3 55.3
Male 30 158.7 2 78.7 0 0.0 0 0.0 8 151.3
Jul-Dec 2011
Female 27 0 1 0 5
Male 58 2 1 1 12
Total 86 120.0 2 20.0 2 23.7 1 30.2 17 79.4
Quarter Sex
District
Darwin Katherine East Arnhem Barkly Alice Springs
Figure B.7.2 Annualised notification rate of hepatitis C by age groups, NT, Jul-Dec 2011
0 60 120 180 240 300 360
15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60+
Age group Annualised notification rate (per 100,000 population)
Female Male All
The majority (78.2%) of the notifications were recorded in the Darwin District (Table B.7.3). Darwin also recorded the highest notification rate in this reporting period. Two non-conjoining age groups (30-34 and 55-59) recorded the highest age-specific rates in males (Figure B.7.2). In females, the highest rate was recorded in the 55-59 year age group, followed by the 35-39 year age group.
Enhanced surveillance data:
A total of 208 notifications of unspecified hepatitis C infection were investigated through the enhanced surveillance system in 2011. However, collection of enhanced surveillance form was successful in only 58 of these cases. The response rate of 27.9% was significantly lower than the 57.2% reported for 2010.
Among the 58 cases with enhanced data, 18 (31.0%) indicated that they were diagnosed longer than two years ago (in or outside of the NT). After deducting these 18 cases, only 40 cases qualified as true unspecified cases. The data on risk factors for these two groups are summarised in Table B.7.4. Notably, the distribution of cases in categories of injection drug use was similar in both groups. In both groups, approximately 1/3 of cases were classified as ‘unknown’.
Table B.7.4 Demographic and injection drug use data for those notified for hepatitis C infection investigated by the enhanced surveillance system in the NT, 2011
Category Unspecified
Previously diagnosed Sex
Female 11 27.5% 6 33.3%
Male 29 72.5% 12 66.7%
Injection drug use
<two years 2 5.0% 1 5.6%
>two years 13 32.5% 6 33.3%
unknown 14 35.0% 6 33.3%
never 11 27.5% 5 27.8%
Total 40 18
B.8 Human Immunodeficiency Virus (HIV)
Six new notifications of HIV were recorded in this reporting period, five males and one female. The demographic and exposure data for cases notified in 2011 are summarised in Table B.8.1.
In 2011, a total of 11 cases were notified with 3 of them classified as newly acquired cases (1 female and 2 males). Three cases were Aboriginal. Five cases were
classified as late presentation cases (45.5%, 66.7% in Aboriginal cases and 37.5% in non-Aboriginal ones). Three patients were born in other countries and acquired HIV before coming to Australia and all of them acquired the infection via heterosexual contact (Table B.8.2). Of the 5 cases in the heterosexual exposure category, only one was confirmed to have acquired from an NT local contact.
The annual number of HIV notifications had remained low in the last five years (see Figure B.8.1).
Table B.8.1 Demographics and exposure categories for HIV cases, NT, 2011
Category Jan-Jun Jul-Dec Total %
Sex
Male 5 5 10 90.9%
Female 0 1 1 9.1%
Total 5 6 11
Ethnicity
Aboriginal 1 2 3 27.3%
Non-Aboriginal 4 4 8 72.7%
Exposure category
Male homosexual contact 1 1 2 18.2%
Male homosexual / bisexual
contact 1 1 2 18.2%
Heterosexual contact 2 3 5 45.5%
Undermined 1 1 2 18.2%
Figure B.8.1 HIV notifications in the NT, 2007-2011
0 5 10 15 20
2007 2008 2009 2010 2011
Number of notifications
Male Female
Table B.8.2 Place of infection by sex for HIV cases notified in 2011, NT Place of infection Female Male Total
NT 1 3 4
Overseas 0 3 3
Unknown 0 4 4
Total 1 10 11
D. Readers’ responses
The SHBBVU is very interested in readers’ responses to this report. Please forward any comments or suggestions to:
Surveillance Project Officer Acting Head of Sexual Health and BBV Unit
Jiunn-Yih Su Dr Nathan Ryder
Sexual Health and BBV Unit, Centre for Disease Control Department of Health PO Box 40596, Casuarina Northern Territory, 0811 Phone: (08) 89228874 Fax: (08) 8922 8809
Email: [email protected], [email protected]
All data in this report are provisional and subject to future revision.
This report is downloadable in PDF format from the website of the Department of Health and Families:
http://www.health.nt.gov.au/Centre_for_Disease_Control/Publications/Sexual_Health _Surveillance_Updates/index.aspx
Suggested citation:
Northern Territory Department of Health. Sexual Health and Blood Borne Viruses Unit Surveillance Update. 2011; Vol. 12, No. 2.
