Australia’s notifiable disease status, 2013: Annual report of the National Notifiable Diseases Surveillance System: Part 5

The National Notifiable Diseases Surveillance System monitors the incidence of an agreed list of communicable diseases in Australia. This report analyses notifications during 2013.

Page last updated: 16 October 2015

Results - Part 2 continued

Sexually transmissible infections

Overview

In 2013, the STIs reported to the NNDSS were chlamydial infection, donovanosis, gonococcal infection and syphilis. Other national surveillance systems that monitor STIs in Australia include the Australian Gonococcal Surveillance Programme (AGSP), which is a network of specialist laboratories monitoring antimicrobial susceptibility patterns of gonococcal infection; and the Kirby Institute for Infection and Immunity in Society.

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Chlamydial infection

  • 82,526 cases of chlamydial infection were notified in 2013.
  • 2013 notification rates were similar to 2012.
  • Women under 25 years of age and Aboriginal and Torres Strait Islander people were disproportionately represented in the notifications of chlamydial infection.

Genital chlamydial infection is caused by the bacterium Chlamydia trachomatis serogroups D–K. Screening is important in detecting chlamydial infections, as a large proportion of infections are asymptomatic. Chlamydial infection is highly treatable, although reinfection is common.43 If left untreated, complications such as epididymitis in males and infertility and pelvic inflammatory disease in females can arise.21

Epidemiological situation in 2013

Chlamydial infection was the most frequently notified disease to the NNDSS (37% of all notifications in 2013), with 82,526 cases (357 per 100,000) notified in 2013. Between 2008 and 2010, notification rates for chlamydial infection increased by 24% (from 272 to 337 per 100,000) but remained relatively stable between 2010 and 2013 (from 337 to 357 per 100,000) (Figure 18).

Figure 18: Notified cases and notification rate for chlamydial infection, Australia, 2008 to 2013, by year

line and bar chart. A link to a text description follows.

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Geographical distribution

In 2013, the notification rate for chlamydial infection was almost 3.5 times higher in the Northern Territory (1,243 per 100,000) than nationally (357 per 100,000). This variation is mostly explained by the relatively large number of Aboriginal and Torres Strait Islander people in the Northern Territory, who have higher notification rates for chlamydial infection than the general population (Figure 19). In the remaining jurisdictions notification rates ranged between 281 per 100,000 in New South Wales and 466 per 100,000 in Western Australia (Figure 20).

Figure 19: Age standardised notification rate for chlamydial infection, selected states and territories,* 2008 to 2013, by year and Indigenous status

line chart. A link to a text description follows.

* Includes the states and territories where Indigenous status was reported for more than 50% of cases between 2008 and 2013: excludes New South Wales.

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Figure 20: Notified cases and notification rate for chlamydial infection, Australia, 2013, by state or territory

line and bar chart. A link to a text description follows.

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Age and sex distribution

Nationally in 2013, the notification rate for chlamydial infection was 302 per 100,000 in males, and 410 per 100,000 in females. The notification rates for males and females remained relatively stable over the past year, from 307 and 419 per 100,000 respectively in 2012. From 2008 to 2013, notification rates increased 37% for males and 28% for females. In 2013, chlamydial infection occurred predominately among those in the 15–29 years age range, accounting for 79% of notified cases.

In 2013, notification rates in females exceeded those in males for those under the age of 30 years, especially for those in the 15–19 years age group (F:M, 3.03:1) and in the 20–24 years age group (F:M, 1.58:1). However, in the 30+ years age groups males had higher rates than females (Figure 21). The overall higher rate among females may be partly attributable to preferential testing of women attending health services compared with men.9,44

Figure 21: Notification rate for chlamydial infection, Australia, 2013, by age group and sex*

bar chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported and notifications where the case was aged less than 13 years.

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When considering notification rates over time in the high risk age groups (15–39 years), they have increased overall since 2008, with slight declines from 2011 to 2013 for females (from 1,771 to 1,707 per 100,000) and from 2012 to 2013 for males (from 1,028 to 1,011 per 100,000) (Figure 22).

Figure 22: Notification rate for chlamydial infection in persons aged 15 to 39 years, Australia, 2008 to 2013, by year and sex* and age group

line and bar chart. A link to a text description follows.

* Excludes notifications for whom age and/or sex were not reported and notifications where the case was aged less than 13 years.

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Indigenous population

The completeness of Indigenous status identification in the notification data varies by year and by jurisdiction. Nationally in 2013, data on Indigenous status were complete for 38% of notifications, which is markedly lower than the preceding 5-year average of 50% (range: 49%–51%). Five jurisdictions had greater than 50% completeness of the Indigenous status field across the 2008 to 2013 period: the Northern Territory, Queensland, South Australia, Tasmania, and Western Australia. Among these jurisdictions, the combined age-standardised notification rate ratio between Indigenous and non-Indigenous populations in 2013 was 3.0:1. Overall, the ratio has varied little over the previous 5 years (range: 2.8–3.2).

Among the Indigenous population, the age-standardised notification rate declined from 2008 to 2009 (from 1,195 to 1,116 per 100,000), increased from 2010 and 2011 (from 1,360 to 1,383 per 100,000), which was followed by another decline from 1,339 per 100,000 in 2012 to 1,327 per 100,000 in 2013. Overall, the age-standardised rates in 2013 were 11% higher than in 2008 (1,195 per 100,000).

Age-standardised notification rates among the non-Indigenous population have decreased by 23% from 2008 (294 per 100,000) to 2013 (226 per 100,000). Between 2012 and 2013, age-standardised notification rates for chlamydial infection in the Indigenous population decreased in Queensland by 6% (from 1,350 to 1,268 per 100,000) and in Western Australia by 5% (from 1,503 to 1,435 per 100,000). Conversely, rates increased in the Northern Territory by 10% (from 1,740 to 1,915 per 100,000), in South Australia by 6% (from 753 to 802 per 100,000) and in Tasmania by 15% (from 134 to 154 per 100,000).

Between 2012 and 2013, the age-standardised notification rates for chlamydial infection in the non-Indigenous population increased by 10% in the Northern Territory (from 436 to 482 per 100,000), by 4% in Queensland (from 344 to 357 per 100,000), and by 7% in South Australia (from 286 to 305 per 100,000). In the same period, age-standardised notification rates decreased 13% in Tasmania (from 375 to 325 per 100,000) and by 4% in Western Australia (from 403 to 388 per 100,000) (Figure 19).

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Donovanosis

  • No cases of donovanosis were notified in 2013.
  • This disease is now rare in Australia.

Donovanosis, caused by the bacterium Klebsiella granulomatis, is a chronic, progressively destructive infection that affects the skin and mucous membranes of the external genitalia, inguinal and anal regions.45 Donovanosis was targeted for elimination in Australia through the National Donovanosis Elimination Project 2001–2004.46 The disease predominantly occurred in Aboriginal and Torres Strait Islander females in rural and remote communities in central and northern Australia. It is now rare, with fewer than 17 cases notified each year since 2002, and fewer than 6 cases notified each year since 2006.

Epidemiological situation in 2013

In 2013, no cases of donovanosis were notified in Australia (Figure 23).

Figure 23: Notified cases of donovanosis, Australia, 1991 to 2013, by year

line chart. A link to a text description follows.

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Gonococcal infection

  • 14,942 cases of gonococcal infection were notified in 2013.
  • Notification rates for gonococcal infection continue to increase.
  • Notifications in 2013 occurred predominately in males aged 20–39 years.

Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae, which affects the mucous membranes causing symptomatic and asymptomatic genital and extra-genital tract infections.21 If left untreated, it can lead to pelvic inflammatory disease in women and infertility in both men and women. Gonococcal infection also increases the risk of both acquisition and transmission of HIV.45

Epidemiological situation in 2013

In 2013, there were 14,942 cases of gonococcal infection reported to the NNDSS, a notification rate of 65 per 100,000. This was a 6% increase compared with the rate reported in 2012 (61 per 100,000). Overall, gonococcal infection notification rates increased by 81% from 2008 (36 per 100,000) to 2013 (65 per 100,000), at an average of 13% each year (range: 6%–23%) (Figure 24).

Figure 24: Notified cases and notification rate for gonococcal infection, Australia, 2008 to 2013, by year

bar and line chart. A link to a text description follows.

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Geographical distribution

In 2013, the notification rate for gonococcal infection was 12.5 times higher in the Northern Territory (811 per 100,000) than nationally (65 per 100,000) (Figure 25). This variation is partly explained by the relatively large number of Aboriginal and Torres Strait Islander people in the Northern Territory, who have higher notification rates for gonococcal infection than the general population (Figure 26).

Figure 25: Notified cases and notification rate for gonococcal infection, Australia, 2013, by state or territory

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Figure 26: Age-standardised notification rate for gonococcal infection, selected states and territories,* 2008 to 2013, by year and Indigenous status

line chart. A link to a text description follows.

* Includes the states and territories where Indigenous status was reported for more than 50% of cases between 2008 and 2013: excludes New South Wales.

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Age and sex distribution

Nationally in 2013, the notification rate for gonococcal infection was 91 per 100,000 in males and 38 per 100,000 in females, which represented a slight increase from 2012 (84 per 100,000 in males and 36 per 100,000 in females). In 2013, gonococcal infection occurred predominately among those aged 15–34 years, who accounted for 72% of notified cases.

Overall, the male to female ratio was 2.4:1 in 2013, which has not changed from 2012. In 2013, notification rates in females exceeded those in males in the under 20 years age groups, but was the reverse for all age groups above 20 years (Figure 27).

Figure 27: Notification rate for gonococcal infection, Australia, 2013, by age group and sex*

bar  chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported and notifications where the case was aged less than 13 years and the infection was able to be determined as non-sexually acquired.

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When considering trends over time in those aged 15–49 years, notification rates increased from 2008 to 2013 in all age groups across both sexes, with the exception of females in the 15–19 years age group, where rates declined between 2011 and 2013 (Figure 28).

Figure 28: Notification rate for gonococcal infection in persons aged 15 to 49 years, Australia, 2008 to 2013, by year and sex and age group*

line chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported.

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Indigenous population

The completeness of Indigenous status identification in the notification data varies by year and by jurisdiction. Nationally in 2013, data on Indigenous status were complete for 72% of notifications, which was higher than the preceding 5–year average of 68% (range: 66%–73%). All states and territories except New South Wales had greater than 50% completeness of the Indigenous status field across the 2008 to 2013 period. Among these states and territories, the combined age-standardised notification rate ratio between Indigenous and non-Indigenous populations in 2013 was 18.5:1, declining from 21.3:1 in 2012. Overall, the rate ratio has declined by 51% from 2008 to 2013 (from 37.6:1 to 18.5:1).

Among the Indigenous population, the age-standardised notification rate increased by less than 1% from 2012 to 2013 (from 770 to 773 per 100,000). Rates in 2013 were 4% lower than in 2008 (745 per 100,000).

The age-standardised notification rate among the non-Indigenous population has more than doubled from 2008 to 2013 (20 and 42 per 100,000 respectively). The average annual increase over this period was 16% (range: 11%–19%).

In terms of geographical trends, age-standardised notification rates for gonococcal infection in the Indigenous population between 2012 and 2013 both increased and decreased among the states and territories in which Indigenous status was more than 50% complete; rates decreased in the Australian Capital Territory by 6% (from 15 to 14 per 100,000), in Queensland by 17% (from 494 to 410 per 100,000), in Victoria by 28% (63 to 45 per 100,000) and in Western Australia by 4% (from 1,086 to 1,044 per 100,000). Conversely, notification rates increased in the Northern Territory by 9% (from 1,827 to 1,991 per 100,000), and in South Australia by 45% (from 515 to 745 per 100,000). Tasmania reported no cases in 2012 but a notification rate of 2.75 in 2013 (Figure 26).

Between 2012 and 2013, the age-standardised rates for gonococcal infection in the non-Indigenous population increased by 23% in the Australian Capital Territory (from 22 to 26 per 100,000), by 4% in the Northern Territory (from 85 to 88 per 100,000), by 15% in Queensland (from 35 to 40 per 100,000), by 62% in South Australia (from 19 to 31 per 100,000), by 98% in Tasmania (from 8 to 15 per 100,000), and by 21% in Victoria (from 42 to 51 per 100,000). Conversely, notification rates decreased in Western Australia by 13% (from 38 to 33 per 100,000) (Figure 26).

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Microbiological trends

The AGSP is the national surveillance system for monitoring the antimicrobial resistance of N. gonorrhoeae isolates. These results are published in more detail in the AGSP annual report in CDI.47

In 2013, the AGSP reported that a total of 4,896 gonococcal isolates were referred for antibiotic susceptibility testing, representing 33% of gonococcal infection notified to the NNDSS. This was slightly lower than the proportion of NNDSS cases tested in 2012 (35%), and a further decrease from the 40%–42% referred in 2008 to 2010.

Eighty-two per cent of the isolates (n=4,032) were from males and 18% (n=862) were from females (M:F, 4.7:1). There were 2 isolates for which gender was unknown. The proportion of gonococcal isolates from males and females tested by the AGSP has remained similar over recent years (<1% variation).

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Syphilis (non-congenital categories)

  • 3,474 cases of syphilis (non-congenital categories) were notified in 2013, a rate of 15.0 per 100,000.
  • In 2013, the notification rate for infectious syphilis was 7.6 per 100,000 and the notification rate for syphilis of more than 2 years or unspecified duration was 7.4 per 100,000.

Syphilis, caused by the bacterium Treponema palladium, is characterised by a primary lesion, a secondary eruption involving skin and mucous membranes, long periods of latency and late lesions of skin, bone, viscera, cardiovascular and nervous systems.21

In 2004, all jurisdictions except South Australia began reporting non-congenital syphilis infections to the NNDSS, separately categorised as: infectious syphilis (primary, secondary or early latent) of less than 2 years duration; and syphilis of more than 2 years or unknown duration. From 2004 to 2011, South Australia reported only cases of infectious syphilis, and then in 2012 commenced reporting syphilis of more than 2 years or unknown duration. Data for all states and territories are reported by diagnosis date, except Queensland, which is reported by notification receive date.

Epidemiological situation in 2013

In 2013, a total of 3,474 cases of syphilis (non-congenital) were reported. This represents a rate of 15.0 per 100,000, a 15% increase compared with 2012 (13.0 per 100,000) (Figure 29). In 2013, 49% of syphilis notifications were categorised as greater than 2 years or unknown duration, and 51% of cases were categorised as less than 2 years duration.

Figure 29: Notification rate for non-congenital syphilis infection (all categories),*,† Australia, 2008 to 2013, by year and category

bar and line chart. A link to a text description follows.

* For infectious syphilis, excludes notifications where the case was aged less than 13 years and the infection was able to be determined as non-sexually acquired. For syphilis of more than 2 years or unknown duration, excludes all notifications where the case was aged less than 13 years.

† For syphilis of more than 2 years or unknown duration, excludes South Australia from 2008–2011.

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Syphilis – infectious (primary, secondary and early latent), less than 2 years duration
  • 1,768 cases of infectious syphilis were notified in 2013.
  • In 2013, 79% of all notifications occurred in males aged 20–54 years. Notification rates in males exceeded those in females in almost all age groups.
  • Cases of infectious syphilis were almost completely in men who have sex with men.
Epidemiological situation in 2013

In 2013, 1,768 notified cases of infectious syphilis (primary, secondary and early latent), less than 2 years duration, were reported to the NNDSS, representing a rate of 7.6 per 100,000. This was an 11% increase compared with the rate reported in 2012 (6.9 per 100,000). The notification rate for infectious syphilis increased overall by 23% from 2008 to 2013 (from 6.2 to 7.6 per 100,000) (Table 6).

Geographical description

In 2013, notification rates for infectious syphilis (less than 2 years duration) were highest in Victoria, the Northern Territory and New South Wales (11.4, 9.1 and 8.1 per 100,000 respectively) (Table 5).

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Age and sex distribution

Nationally in 2013, the notification rate for infectious syphilis was 14.0 per 100,000 in males and 1.3 per 100,000 in females, a male to female rate ratio of 11.0:1. In males, this was an increase of 12% when compared with the 2012 rate (12.4 per 100,000) and in females this was a decrease of 5% compared with the 2012 rate (1.3 per 100,000). In 2013, 79% of all notifications occurred in males aged 20–54 years, and notification rates for males exceeded those for females in almost all age groups (Figure 30). Diagnoses of infectious syphilis in 2013 were almost completely confined to men who have sex with men.28

Figure 30: Notification rate for infectious syphilis (primary, secondary and early latent), less than 2 years duration, Australia, 2013, by age group and sex*

bar chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported and notifications where the case was aged less than 13 years and the infection was able to be determined as non-sexually acquired.

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Notification rates for males aged 15 years or over increased overall among most age groups from 2008 to 2013. An exception was the 35–39 years age group, for which the rate declined overall from 2008 to 2013 (from 27 to 26 per 100,000) (Figure 31).

Figure 31: Notification rate for infectious syphilis (primary, secondary and early latent), less than 2 years duration, in persons aged 15 years or over,* Australia, 2008 to 2013, by year and sex and age group*

line chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported.

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In females aged 15 years or over, notification rates between 2008 and 2013 have averaged 2.1 per 100,000 (range: 0.3–3.9). Over the 6-year period, the notification rates remained low for females across all age groups.

Indigenous population

The completeness of Indigenous status identification in the notification data varies by year and by jurisdiction. Nationally in 2013, data on Indigenous status were complete for 72% of notifications, an increase compared with 2012 (66% complete) and higher than the preceding 5–year average of 68% (range: 66%–73%). All states and territories except New South Wales had greater than 50% completeness of the Indigenous status field across the 2008 to 2013 period.

Among the states and territories with greater than 50% completeness for Indigenous status, the combined age standardised notification rate ratio between the Indigenous and non-Indigenous populations in 2013 was 3.7:1, which was lower than the preceding 5–year average of 7.6:1 (range: 5.7–9.3).

The age-standardised notification rate in the Indigenous population declined from 34 per 100,000 in 2012 to 25 per 100,000 in 2013. Overall, 2013 rates are 41% lower than 2008 rates (41 per 100,000). This declining trend is not seen in all jurisdictions (Figure 32) but it is likely that programs that include population screening and case management, supported by centrally based state-wide syphilis registers, are making some progress towards elimination of infectious syphilis in Indigenous communities.48

Figure 32: Age-standardised notification rate for infectious syphilis (primary, secondary and early latent), less than 2 years duration, selected states and territories,* 2008 to 2013, by Indigenous status and year

line chart. A link to a text description follows.

* Includes the states and territories where Indigenous status was reported for more than 50% of cases between 2008 and 2013: excludes New South Wales.

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The age-standardised notification rate in the non-Indigenous population has increased from 6.0 per 100,000 in 2012 to 6.6 per 100,000 in 2013. The rate in 2013 was 32% higher than it was in 2008 (5.0 per 100,000).

In terms of geographical trends, from 2012 to 2013, the age-standardised rates for syphilis infection in the Indigenous population declined in all states and territories except Victoria and Tasmania (Figure 32). Between 2008 and 2013, the Northern Territory was the only jurisdiction to report declining Indigenous age-standardised notification rates every year. The increase evident in Indigenous notification rates in Western Australia in 2008 was largely attributable to an outbreak that occurred in the Pilbara region among Aboriginal people during that year.49

Among the non-Indigenous population between 2012 and 2013, the age-standardised rates for syphilis infections increased in all jurisdictions except the Australian Capital Territory and Queensland (Figure 32).

Syphilis of more than 2 years or unknown duration
  • 1,706 cases of syphilis of more than 2 years or unknown duration were notified in 2013.
  • Overall, notification rates have increased from 6.3 per 100,000 in 2008 to 7.4 per 100,000 in 2013.
  • The notification rate among males (10.8 per 100,000) was more than double that for females (3.9 per 100,000) in 2013.
Epidemiological situation in 2013

In 2013, 1,706 cases of syphilis of more than 2 years or unknown duration were reported to the NNDSS. This represents a notification rate of 7.4 per 100,000. Overall, notification rates have increased by 17% from 2008 to 2013 (6.8 to 7.4 per 100,000) (Table 6).

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Geographical distribution

In 2013, notification rates for syphilis of more than 2 years or unknown duration were highest in the Northern Territory (39.0 per 100,000), followed by Victoria (9.8 per 100,000) (Table 5).

Age and sex distribution

Nationally in 2013, the notification rate for syphilis of more than 2 years or unknown duration was 10.8 per 100,000 for males and 3.9 per 100,000 in females, a male to female ratio of 2.8:1. In males, this was an increase of 30% when compared with the 2012 rate (8.3 per 100,000), and in females a 4% increase from the 2012 rate (3.8 per 100,000). Around 71% of all notifications occurred in males aged 20 years or over, and notification rates in males exceeded those in females in all age groups (Figure 33).

Figure 33: Notification rate for syphilis of more than 2 years or unknown duration,* Australia, 2013, by age group and sex

bar chart. A link to a text description follows.

* Excludes notifications for whom age and or sex were not reported and notifications where the case was aged less than 13 years and the infection was able to be determined as non-sexually acquired.

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Notification rates for those aged 15 years or over from 2008 to 2013 increased overall in most age groups for males, and declined overall across all age groups for females (Figure 34).

Figure 34: Notification rate for syphilis of more than 2 years or unknown duration, in persons aged 15 years or over,* Australia,† 2008 to 2013, by year and sex and age group

line chart. A link to a text description follows.

* Excludes notifications where age and/or sex were not reported.

† Data from all states and territories except South Australia in 2008–2011.

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Congenital syphilis

  • Seven cases of congenital syphilis were notified in 2013.
  • Congenital syphilis remains rare in Australia.

Congenital syphilis is caused by foetal infection with the bacteria T. pallidum. Syphilis is acquired by infants either in-utero or at birth from women with untreated early infection. Infections commonly result in abortion or stillbirth and may cause the death of a newborn infant. Congenital syphilis can be asymptomatic, especially in the first weeks of life.21

Epidemiological situation in 2013

There were 7 notifications of congenital syphilis in 2013, which remains low after a decrease observed over the 10 years prior (Figure 35). Antenatal screening for syphilis with follow-up and adequate treatment is considered to be a contributor to this decline.48

Figure 35: Notified cases of congenital syphilis, Australia, 2003 to 2013, by year

line chart. A link to a text description follows.

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