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Discussion

This review of LabVISE data for the last 10 years has shown that this reporting scheme contains valuable data potentially important to public health in Australia. LabVISE collects important data on the viral diseases, particularly those of children that are not reported in other surveillance systems. These data supplement diseases under surveillance through the National Notifiable Diseases Surveillance System.

LabVISE has had a uniquely important role in the control of two diseases in the last 10 years, influenza and poliomyelitis.

Influenza epidemics occur in Australia annually in winter. Admissions to hospitals in Australia for influenza and pneumonia exceed 250,000 annually.⁵⁰ Pneumonia secondary to influenza infection in the elderly is an important cause of mortality.^36,50 For this reason, the Australian Government has provided influenza vaccination free of charge to Australians aged 65 years and above since 1999. Surveys of elderly Australians in 2000 and 2001 show that 77 per cent of this age group are taking annual influenza vaccination.⁵¹ Each year, the composition of the Australian influenza vaccine is reviewed and altered to reflect the virus strains circulating in the previous influenza season. This information is derived in a large part from isolates collected through LabVISE laboratories.

Laboratory reports of influenza are reported throughout the year and allow surveillance of the annual epidemics. These data, combined with reports of influenza-like illness in sentinel general practices, are reported annually in the report of the National Influenza Surveillance Scheme.⁵²

Since June 2001, influenza data are published fortnightly throughout the year on the Communicable Diseases Australia Website at http://www1.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm. It is essential for influenza surveillance and for vaccine production that LabVISE laboratories continue to isolate and characterise influenza viruses. The pandemic action plan it is only a matter of time until genetic mutations in the influenza virus trigger an influenza pandemic. Laboratory surveillance will be critical in the early stages of a pandemic to characterise the new virus and to monitor the geographical spread.

The last case of poliomyelitis in Australia was reported in 1972 and the Western Pacific Region was declared polio-free in October 2000. The WHO recommends continued surveillance of poliovirus in Australia, including laboratory investigations of all cases of acute flaccid paralysis and vaccine-associated paralytic polio and the monitoring of circulating enteroviruses in the community and intratypic differentiation of all polioviruses.³² LabVISE contributes significantly to these aspects of polio surveillance. Such surveillance is still not reaching the targets set by WHO³² and surveillance needs to continue until the global eradication of poliomyelitis is achieved. Recent outbreaks of polio in Bulgaria,⁵³ show that countries that have eliminated endemic polio are at risk from imported polio cases.

LabVISE has accumulated important information on viral pathogens of public health importance, particularly causative organisms of viral meningitis, viral gastroenteritis and viral respiratory diseases.
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Viral meningitis surveillance is recommended by the WHO.⁵⁴ The rationale for this surveillance is that viral meningitis can occur in epidemics as well as sporadically and that although mortality is generally low, the associated morbidity and risk of long term sequelae in children are high. Laboratory identification of the causative virus and measurement of incidence by time, geographical area and age group are important to the identification and control of epidemics. There is no other national surveillance system in Australia, other than LabVISE, in a position to undertake this surveillance.

Outbreaks of viral meningitis associated with echovirus 11 and 30, enterovirus 71, and coxsackie A9 and B5, have been detected in Australia in recent years. However, there has been no internally coordinated approach to these important public health problems.

Viral agents are responsible for the largest proportion of gastroenteritis in developed countries.⁵⁵ Rotavirus is a major cause of diarrhoea and may be an important cause of gastroenteritis in the elderly. In Australia, there are annual epidemics in the winter months and large outbreaks have occurred biennially in the Northern Territory.⁵⁶ During these epidemics, hospital consultations and admissions are greatly increased. Although deaths are rare in industrialised countries, rotavirus causes 800,000 childhood deaths annually in the developing countries.⁵⁷ The introduction of a rotavirus vaccine in 1998 was to be an important milestone in the control of this disease. The vaccine was subsequently withdrawn after cases of intestinal intussusception. Despite this, vaccination for rotavirus, particularly as part of the childhood immunisation program in developing countries, remains a priority. Since 1999, the National Rotavirus Surveillance Program has serotyped rotaviruses isolated in laboratories, measured the emergence of new serotypes, and tracked their geographical spread in Australia.⁴⁰ Continued laboratory surveillance of rotavirus is important to monitor epidemics, to monitor circulating serotypes and to measure the impact of future vaccines.

Norwalk-like virus has emerged as a major cause of gastroenteritis in adults. The control of this agent is difficult, as transmission has been shown to be by aerosols and environmental contamination⁵⁸ as well as by contaminated food.⁴² The epidemiology of the virus continues to be elucidated and surveillance of this agent is important for the control of community gastroenteritis.

Viral respiratory diseases include influenza, parainfluenza, respiratory syncytial virus and various adenoviruses. These viruses are important childhood pathogens. The importance of LabVISE to surveillance of influenza in Australia has been noted above. More common childhood infections with parainfluenza and RSV have been reported consistently to LabVISE over the years. Both viruses cause annual epidemics, with parainfluenza serotype 1 showing annual epidemics while serotypes 2 and 3 show biennial epidemics.

Since HPIV-3 causes more severe disease, monitoring of parainfluenza serotypes is important. Adenoviruses play a role in acute respiratory infections and monitoring of circulating serotypes will be an important activity to predict disease patterns in the Australian community.

The LabVISE scheme has been evaluated elsewhere³⁰ and a full discussion of the schemes strengths and weaknesses belong to another paper. However, it is obvious from the analysis performed here that there are limitations to the value of LabVISE data. As has been noted earlier the representativeness of the data in LabVISE is uncertain since there has been no measure from what population these results are drawn. The large number of reports from children in LabVISE reflects both the nature of the pathogens reported but also the inclusion of reports from major children's hospitals in Australia. By contrast, other age groups may be under-represented. The large proportion of tertiary hospital laboratories in LabVISE also biases the system to report less common pathogens or those more difficult to diagnose, seen perhaps more often in sicker individuals and not typical of the community at large. It is unclear what populations these large reference laboratories serve and laboratories have only reported positive results without reporting on the total number of tests performed. Thus, there are no denominators in the data to calculate rates. The National Respiratory and Enteric Virus Surveillance System of the Centers for Disease Control and Prevention in the USA, collect data as the percentage of positive isolates from laboratories, which allows monitoring of virus activity throughout the year. (www.cdc.gov/ncidod/dvrd/revb/nrcvss/index. Accessed, January 2002).

Another criticism of LabVISE has been the lack of focus, in that the surveillance system covers a large range of pathogens of varying public health significance. A focus on viral agents of meningitis, gastroenteritis and respiratory disease prioritised by public health importance may be an important option for the future of LabVISE. Changes to the pathogens under surveillance and the data collected on each notification in NNDSS impact on the usefulness of data collected by LabVISE. Notifications of measles, mumps, rubella, hepatitis, arboviral infections and chlamydial infection to NNDSS greatly exceed reports to LabVISE. Now that more microbiological data are collected on each NNDSS notification, the data collected by LabVISE has lost its value. Inclusion of these organisms in LabVISE may therefore be redundant and this supports the option that LabVISE should focus on a supplementary set of pathogens.

Reporting of LabVISE data has been poor for many years. This is the first full analysis of LabVISE data since 1996. The timeliness of reports through Communicable Diseases Intelligence is also poor as the publication schedule has changed to quarterly. Publication of reports on the Internet would be important in giving timely information.

The quality of data has declined over time with less complete identification of pathogens. A data collection system for NNDSS, which allows the updating of reports with additional detail, is being implemented. This allows the timely notification of a case and the subsequent completion of details including laboratory results. A similar system for LabVISE would allow timely reporting and complete characterisation of the pathogen.

This review of the last 10 years of LabVISE data shows that much valuable data has been accumulated and lessons learnt. With a new focus and commitment, LabVISE will continue to have an important role in public health in Australia.


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