Some viruses infected floppy disks so that systems were infected when the disks were read.
On the other hand, some viruses have caused so much damage that a simple reinstallation of the operating system was insufficient to repair them.
While Live OneCare did manage to spot 100% of the macro viruses it was tested against, it missed some wild viruses, polymorphic programs and file infectors.
"These studies show that RSV is a 'hit and hide' virus, rather like HIV or some hepatitis viruses, " said Professor Peter Openshaw of Imperial College and one of those involved in the study.
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Some of these viruses have also been reported to cross the species barrier and cause disease or sub-clinical infections in humans.
Some spam messages contain computer viruses that wreak havoc with the recipients' hard drives.
And the other issue is that, for the moment at least, getting these magic factors into the skin cells requires using viruses, retroviruses, some other things that you don't want to put in cells.
Most of the viruses are harmless, but some are potentially deadly when passed to humans.
Hundreds of viruses exist, but only some cause visible symptoms and debilitating diseases.
In some cases, said the researchers, viruses could be spread by household pets such as cats and dogs that are injected with the tags to help identify their owner.
It may be that they belong to some as-yet-uncharacterised group of viruses (entities classified outside Linnaeus's system, since there is no agreement about whether they are alive or not).
Also, viruses and bacteria can live for hours on some surfaces some viral particles have been found to be active up to a day in certain places.
Some factors behind this year's outbreak include a higher mosquito population and "fitter viruses with higher epidemic potential, " said according to Ng Lee Ching, director of the Environmental Health Institute at Singapore's National Environment Agency.
These genes are also linked to fighting tumours in humans and the study could help research into preventing some types of cancers in people, which like Marek's disease, are caused by viruses.
As the 1980s charged on, more computer viruses were written and became an increasing problem until antivirus software was invented and eventually provided some degree of protection.
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