Australia at epicentre of virus test kit
UARANTINE officials, scientists and doctors will soon have a new tool in their battle against dangerous bugs — a quick and easy test able to detect all the so-called flaviviruses, which cause serious diseases such as dengue fever and Japanese encephalitis.
Team leader Mark Gibbs says pathology laboratories worldwide will be able to run the test using conventional DNA testing equipment as soon as details are published. His colleague at the University of Queensland in Brisbane, doctoral student Sheryl Maher, is preparing a report of the work, a joint effort of the Australian National University, the University of Queensland, Britain’s Oxford University and the Australian Biosecurity Cooperative Research Centre.
Already, quarantine officials in the Top End are interested. ‘‘ If you come into Australia with dengue, they want to stop you in your tracks,’’ says Gibbs, a virologist, expert in bioinformatics and Australian Research Council researcher at Canberra’s ANU. ‘‘ And if you have an unknown flavivirus, they’re going to want to bring in the men with the white biosecurity suits.’’
Existing flavivirus tests are slow, often unreliable and unable to detect all of the 53 known flavivirus species, let alone identify unknown viruses falling into the group, or genus. What’s more, doctors often confuse signs of flavivirus infection with similar symptoms of other common infections such as influenza or septicaemia. If people have mild or subclinical symptoms they may not seek treatment, not only potentially spreading the disease but possibly resulting in a more severe illness for themselves.
‘‘ So early and accurate diagnosis is very important,’’ Gibbs says.
The approach taken by his team involved searching through 257 versions of the genome, or full genetic complement , of known flaviviruses. They discovered two stretches of genetic material that were the same in all those flaviviruses.
Using that information the scientists designed two ‘‘ primers’’, stretches of singlestranded DNA (RNA) that attach to RNA from a flavivirus but not to non-flavivirus RNA. They tested the primers on the known species, as well as on samples of flaviviruses collected 40 years ago which are now not detectable by any existing test.
Since the primers picked up all the flaviviruses, Gibbs is confident they will identify any emerging or previously unidentified species in the group. As a result, once laboratories have the sequence of the primers — the genetic building blocks of the primers — they’ll be able to detect all members of the group. Technicians would use the primers in standard polymerase chain reaction tests like those regularly utilised in forensic DNA tests.
Gibbs, Maher and their co-workers decided to develop the flavivirus detection test to help avert outbreaks of unknown viruses such as severe acute respiratory syndrome (SARS). In 2003 that new and frightening disease swept through Hong Kong, South-East Asia and China, eventually spreading to North America and Europe. Strict quarantine measures kept SARS out of Australia.
‘‘ It took about a month and the effort of several teams of researchers before we knew what SARS was,’’ Gibbs recalls. SARS was a coronavirus, not a flavivirus as some scientists believed. Still, the experience highlighted the critical need for tests able to identify new and potentially deadly viruses.
And flaviviruses are at the top of the list, says Gibbs. Most come from animals and are initially spread by insects. ‘‘ They may or may not be transmitted to humans, but many in the group have been transmitted to people and some of them are very bad, indeed.’’
According to Gibbs, his colleagues at Oxford had discovered previously unknown viruses on the Great Barrier Reef and are searching for new flaviviruses in samples collected from ticks and mosquitoes from around the world. ‘‘ We’re waiting to see what they are,’’ he said.
Research leader: Mark Gibbs