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Epidemiology of influenza B in Australia: 2001 ‐ 2014 influenza seasons

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ABSTRACT

Background: Influenza B is characterised by two antigenic lineages: B/Victoria and B/Yamagata. These lineages circulate together with influenza A during influenza seasons, with varying incidence from year to year and by geographic region.

Objective: To determine the epidemiology of influenza B relative to influenza A in Australia.

Methods: Laboratory‐confirmed influenza notifications between 2001 and 2014 in Australia were obtained from the Australian National Notifiable Diseases Surveillance System.

Results: A total of 278 485 laboratory‐confirmed influenza cases were notified during the study period, comprising influenza A (82.2%), B (17.1%) and ‘other and untyped’ (0.7%). The proportion of notifications that were influenza B was highest in five‐ to nine‐year‐olds (27.5%) and lowest in persons aged 85 years and over (11.5%). Of all B notifications with lineage determined, 77.1% were B/Victoria and 22.9% were B/Yamagata infections. Mismatches between the dominant B lineage in a season and the trivalent vaccine B lineage occurred in over one‐third of seasons during the study years. In general, influenza B notifications peaked later than influenza A notifications.

Conclusion: The proportion of circulating influenza B in Australia during 2001‐2014 was slightly lower than the global average and was dominated by B/Victoria. Compared with influenza A, influenza B infection was more common among older children and young adults and less common in the very elderly. Influenza B lineage mismatch with the trivalent vaccine occurred about one‐third of the time.

No MeSH data available.


Related in: MedlinePlus

Age‐specific population rate of laboratory‐confirmed influenza A and B notifications in years in which at least 20% of notifications were influenza B, Australia. (A) Top fig: age‐specific notification rate for influenza A (215 notifications of unknown age were excluded from analysis). (B) Bottom fig: age‐specific notification rate for influenza B (37 notifications of unknown age were excluded from analysis)
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irv12432-fig-0003: Age‐specific population rate of laboratory‐confirmed influenza A and B notifications in years in which at least 20% of notifications were influenza B, Australia. (A) Top fig: age‐specific notification rate for influenza A (215 notifications of unknown age were excluded from analysis). (B) Bottom fig: age‐specific notification rate for influenza B (37 notifications of unknown age were excluded from analysis)

Mentions: For seasons in which influenza B represented at least 20% of all notifications, age‐specific notification rates per 100 000 population are shown in Figure 3A,B, for influenza A and B, respectively. Compared with influenza A, higher notification rates of type B were observed in persons aged <20 years and lower rates in persons aged 85 years or more. Compared with other years, 2012 influenza season showed increased influenza activity in the country especially in very young age and the older population.


Epidemiology of influenza B in Australia: 2001 ‐ 2014 influenza seasons
Age‐specific population rate of laboratory‐confirmed influenza A and B notifications in years in which at least 20% of notifications were influenza B, Australia. (A) Top fig: age‐specific notification rate for influenza A (215 notifications of unknown age were excluded from analysis). (B) Bottom fig: age‐specific notification rate for influenza B (37 notifications of unknown age were excluded from analysis)
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Related In: Results  -  Collection

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Show All Figures
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irv12432-fig-0003: Age‐specific population rate of laboratory‐confirmed influenza A and B notifications in years in which at least 20% of notifications were influenza B, Australia. (A) Top fig: age‐specific notification rate for influenza A (215 notifications of unknown age were excluded from analysis). (B) Bottom fig: age‐specific notification rate for influenza B (37 notifications of unknown age were excluded from analysis)
Mentions: For seasons in which influenza B represented at least 20% of all notifications, age‐specific notification rates per 100 000 population are shown in Figure 3A,B, for influenza A and B, respectively. Compared with influenza A, higher notification rates of type B were observed in persons aged <20 years and lower rates in persons aged 85 years or more. Compared with other years, 2012 influenza season showed increased influenza activity in the country especially in very young age and the older population.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Influenza B is characterised by two antigenic lineages: B/Victoria and B/Yamagata. These lineages circulate together with influenza A during influenza seasons, with varying incidence from year to year and by geographic region.

Objective: To determine the epidemiology of influenza B relative to influenza A in Australia.

Methods: Laboratory&#8208;confirmed influenza notifications between 2001 and 2014 in Australia were obtained from the Australian National Notifiable Diseases Surveillance System.

Results: A total of 278&nbsp;485 laboratory&#8208;confirmed influenza cases were notified during the study period, comprising influenza A (82.2%), B (17.1%) and &lsquo;other and untyped&rsquo; (0.7%). The proportion of notifications that were influenza B was highest in five&#8208; to nine&#8208;year&#8208;olds (27.5%) and lowest in persons aged 85&nbsp;years and over (11.5%). Of all B notifications with lineage determined, 77.1% were B/Victoria and 22.9% were B/Yamagata infections. Mismatches between the dominant B lineage in a season and the trivalent vaccine B lineage occurred in over one&#8208;third of seasons during the study years. In general, influenza B notifications peaked later than influenza A notifications.

Conclusion: The proportion of circulating influenza B in Australia during 2001&#8208;2014 was slightly lower than the global average and was dominated by B/Victoria. Compared with influenza A, influenza B infection was more common among older children and young adults and less common in the very elderly. Influenza B lineage mismatch with the trivalent vaccine occurred about one&#8208;third of the time.

No MeSH data available.


Related in: MedlinePlus