The Australian Immunisation Handbook 10th Edition 2013

Figure 4.7.1: Influenza notification rates 2006–2007* and hospitalisation rates
2005–2007,* Australia, by age group 9
Rate per 100 000 population
120
100
80
60
40
20
0
0–4
5–9
10–14
15–19
20–24
Rate per 100 000 population
25–29
250
200
150
100
50
30–34
0
35–39
0 1 2
Age (years)
3 4
40–44
45–49
50–54
Age (years)
55–59
Notifications
Hospitalisations
* Notifications where the month of diagnosis was between January 2006 and December 2007;
hospitalisations where the month of separation was between July 2005 and 30 June 2007. These
data are prior to the appearance of the pandemic A(H1N1)pdm09 virus in 2009.
Three pandemics were recognised in the 20th century, in 1918 (H1N1),
1957 (H2N2) and 1968 (H3N2). Each of these pandemic strains replaced the
previously circulating influenza A subtype and went on to circulate as seasonal
influenza. In 1977, the A (H1N1) re-emerged in the human population and, since
then, A (H1N1) and A (H3N2) have co-circulated with influenza B. Recently,
the avian influenza A virus subtypes, H5N1 and H9N2, have caused human
infections. The most notable of these is the A (H5N1) subtype, which has become
established in domestic poultry throughout Southeast Asia and has spread to
Europe and Africa in either wild birds or domestic poultry. Although growing
numbers of people have contracted the virus by contact with birds and there is
a high mortality rate (≥50%), there has been no evidence of ongoing person-toperson
transmission.
In 2009, the World Health Organization (WHO) declared a pandemic of a novel
subtype A (H1N1) influenza virus, A(H1N1)pdm09, which originated in swine;
the pandemic started in Mexico and the United States in April 2009. In August
2010, the WHO reported that more than 214 countries and overseas territories or
60–64
65–69
70–74
75–79
80–84
85
PART 4 VACCINE-PREVENTABLE DISEASES 245
4.7 INFLUENZA