The meningococcal virus continued to spread in 2020, despite restrictive COVID-19 lockdowns.
A University of Adelaide study showed a rise in the proportion of school leavers with meningococcal bacteria in their throat.
Of 1388 people aged 17 to 25 who attended University of Adelaide orientation events in February and March that year, 3.7 per cent tested positive for meningococcal bacteria.
That rose to 6.8 per cent in August and September.
Professor Helen Marshall said researchers were "quite surprised" with the results.
"We thought it would have decreased following the introduction of COVID-19 containment strategies," she said.
Prof Marshall said vaccinating people against meningococcal remained critical.
Meningococcal can be fatal and kill within hours. Early diagnosis and treatment is vital.
Symptoms include a rash of red or purple pinprick spots, or larger bruise-like areas, that don't turn skin coloured when pressed on.
Others include fever, headaches and sensitivity to light. Smoking, intimate kissing and close contact in pubs, clubs and parties can lead to infection.
Meanwhile, an estimated 31,000 Australian workers are calling in sick every day because of the debilitating symptoms of long-COVID.
Treasury data shows 12 per cent of COVID-related absenteeism is because of the long-term after-effects of the virus.
NSW Premier Dominic Perrottet is pushing to shrink the required seven-day isolation period to five days for people who test positive for COVID.
Mr Perrottet plans to bring it up at next week's national cabinet meeting with his state, territory and federal counterparts.
LATEST 24-HOUR COVID-19 DATA:
NSW: 5636 cases, 22 deaths, 1780 in hospital with 36 in ICU
Victoria: 2935 cases, 25 deaths, 386 in hospital with 18 in ICU
Tasmania: 265 cases, no deaths, 35 in hospital with two in ICU
ACT: 247 cases, no deaths, 112 in hospital with three in ICU
Queensland: 2091 cases, eight deaths, 321 in hospital with 16 in ICU
