Social isolation the way to stop flu spreading

May 3 2009

Australian researchers say isolation would slow down the spread of outbreaks of influenza.

The researchers at the University of Western Australia say their research shows that avoiding contact with other people could greatly reduce the spread of flu.

Their research comes at an opportune time as it offers vital clues to public health authorities in dealing with potential pandemics such as the current "swine flu" (H1N1) outbreak.

The researchers Professor George Milne, Dr. Joel Kelso and Dr. Simon Huband used a computer simulation model to emulate the spread of influenza H5N1 commonly known as 'bird flu', but they say the results are directly applicable to H1N1 (swine flu).

The researchers say imposing "social distancing" measures such as school closures, home isolation, partial closure of workplaces and reduced community contact, if done rapidly, could prevent a local epidemic.

The research team say the timing of activation of such non-pharmaceutical interventions is critical and for a very transmissible strain, application of all four interventions at the same time as the first case is introduced, and enforcing these draconian measures continuously, can potentially hold the illness rate at 16% - compared to 73% if they are not used.

The model used statistical data on the population of Albany, a town of 30,000 people in south-west Western Australia and assumed 100% of infectious children and 90% adults are home quarantined and a 50% reduction in workplace attendance and community-wide contact.

The model was developed by the team from UWA's School of Computer Science and Software Engineering and is believed to be the most detailed replication of an actual community - down to individual schools, employers and the exact make-up of households - to be used to quantify the impact of alternative intervention strategies.

Professor Milne says the model showed that non-pharmaceutical social distancing interventions could reduce the rate of development and the overall burden of epidemics and while such draconian measures will only be mandated under extreme circumstances, given their impact on personal freedom, they appear to play a key role in delaying the development of a ‘worst case' influenza epidemic.

He says social distancing may be critical in holding back an epidemic until vaccines are deployed on a sufficient scale that subsequent relaxation of these measures won't result in an acceleration of the outbreak.

Professor Milne says the measures must be employed as soon as possible if they are to have maximum effect and for an outbreak as infectious as the 1918 Spanish Flu pandemic, a combination of all intervention measures must be introduced within two weeks of the first case appearing in a town or city, to prevent an epidemic developing - delays of two, three and four weeks resulted in final attack rates of 7%, 21% and 45% respectively.

The UWA team has provided reports based on their two published papers to the Commonwealth Department of Health and Ageing (DoHA) and the World Health Organisation (WHO) and received funding from the National Health and Medical Research Council, DoHA and WHO.

The research is published in the current issue of the journal BMC Public Health.