There have been no deaths in Australia from a confirmed spider bite since 1979, according to the Australian Museum.
An effective antivenom for redback spiders was introduced in 1956, and one for funnel-web spiders in 1980. They are the only two spiders that have caused deaths in Australia in the past.
About 2000 people are bitten each year by redback spiders, the Australian Museum says.
NSW Health says redback spider bites are common but very unlikely to prove lethal, even if untreated. They can result in severe pain and symptoms that can continue from hours to days.
The initial bite may only cause mild discomfort or irritation, and sometimes is not even noticed.
Pain usually increases over an hour or two and may radiate up the limb. Abdominal or chest pain may develop, as may pain in other parts of the body.
The pain is persistent and usually severe enough to interfere with normal activities, such as work or sleep.
The duration of effects vary, with only moderate pain for a few hours in some cases, to severe persistent pain for two to five days.
Other symptoms can include nausea, vomiting, headache, malaise and lethargy.