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Results - Part B: Analysis of data by pathogen, continued

Ortho/paramyxoviruses

Influenza virus

Influenza is a highly contagious acute respiratory disease which has caused epidemics and pandemics throughout the world for centuries. While most influenza infections are self-limiting, lower respiratory tract and cardiac complications, particularly in the elderly can lead to increased hospitalisations and deaths, particularly during the epidemic months.³⁶

Up until 2001, LabVISE has been the only source of laboratory-confirmed influenza data for national influenza surveillance. Viral isolates are forwarded to the World Health Organization Centre for Reference and Research on Influenza for subtype and antigenic analysis. These data have been used to monitor circulating influenza viral strains and to determine the composition of the annual influenza vaccine for Australia.

Influenza reports to LabVISE for 1991 to 2000 are shown in Table 31.

Table 31. Laboratory reports to LabVISE of influenza, 1991 to 2000, by strain type and annual influenza A:B ratio

Virus	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Influenza A	60	1,322	544	1,196	797	1,641	1,447	2,746	1,932	1,506	13,191
Influenza B	408	126	648	87	355	79	903	149	279	580	3,614
Ratio influenza A:B	0.1	10.5	0.8	13.7	2.2	20.8	1.6	18.4	6.9	2.6

The monthly reports to LabVISE of influenza A and B, between 1991 and 2000 are shown in Figure 16. Typically, influenza A is predominant with outbreaks of influenza B every alternate year. Laboratory reports of influenza are largely from young children aged under 5 years.

Figure 16. Laboratory reports to LabVISE of influenza A and influenza B infections, 1991 to 2000, by month of specimen collection

Parainfluenza virus

Human parainfluenza viruses (HPIV) are an important cause of acute respiratory infection in infants and children and are especially associated with laryngotracheobronchitis (croup). In the USA, the parainfluenza viruses are responsible for one-third of the estimated 5 million cases of lower respiratory infections occurring annually in children under 5 years of age.³⁷ Infections also occur in older age groups. Four serotypes are recognised. Biennial epidemics of HPIV-1 and HPIV-2 occur in autumn, while HPIV-3 causes annual epidemics, particularly among young infants aged less than 6 months. LabVISE reports of parainfluenza virus are shown in Table 32.

Top of pageTable 32. Laboratory reports to LabVISE of parainfluenza virus, 1991 to 2000, by serotype

Virus	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Parainfluenza virus type 1	47	281	44	548	32	315	61	276	44	230	1,878
Parainfluenza virus type 2	143	60	127	61	178	73	112	30	114	36	934
Parainfluenza virus type 3	556	554	513	526	833	730	962	409	803	516	6,402
Parainfluenza virus type 4	-	-	-	-	2	7	-	3	2	-	14
Parainfluenza virus typing pending	59	80	46	68	36	32	239	5	1	1	567
Total	805	975	730	1,203	1,081	1,157	1,374	723	964	783	9,795

Laboratory reports of parainfluenza by serotype and month between 1991 and 2000 are shown in Figure 17. There are annual epidemics of parainfluenza type 3, while parainfluenza types 1 and 2 occur in biennial epidemics in alternate years in Australia. Laboratory reports to LabVISE for parainfluenza were predominantly for children aged 0-4 years. In 2000, 68 per cent of HPIV-1, 53 per cent of HPIV-2 and 68 per cent of HPIV-3 occurred in children aged 0-4 years.

Figure 17. Laboratory reports to LabVISE of human parainfluenza serotypes 1, 2 and 3, 1991 to 2000, by month of specimen collection

HPIV-1 human parainfluenza serotype 1
HPIV-2 human parainfluenza serotype 2
HPIV-3 human parainfluenza serotype 3

Respiratory syncytial virus

Respiratory syncytial virus (RSV) infects almost all people in all regions of the world within the first years of life and is the major cause of lower respiratory illness in young children. RSV is an important cause of community-acquired pneumonia.³⁸ A recent study from the United Kingdom suggests that RSV infection may be confused with influenza-like illness.³⁹ RSV identifications were the single most common virus reported in LabVISE (14.3% of total between 1991 and 2000). LabVISE reports of RSV are shown in Table 33.

Table 33. Laboratory reports to LabVISE of respiratory syncytial virus, 1991 to 2000

Virus	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	Total
Respiratory syncytial virus	2,555	3,556	3,506	3,749	3,889	4,068	4,588	4,641	3,059	2,735	36,346

RSV epidemics occur annually in the winter months (Figure 18) and most patients are aged between 0-4 years. Thus of 2,735 reports in 2000, 2,446 (89.4%) were in children aged less than 5 years.

Figure 18. Laboratory reports to LabVISE of respiratory syncytial virus infection, 1991 to 2000, by month of specimen collection




This article was published in Communicable Diseases Intelligence Volume 26, No 3, September 2002