The Victorian Department of Health and Human Services said it had identified a number of cases of the infection linked to lettuce grown and packaged by Victorian company Tripod Farmers.

It is sold at Coles, Woolworths, Bi-Lo and other grocers as Coles 4 Leaf Mix, Woolworths salad mix, SupaSalad Supamix and Wash N Toss salad mix.

The affected products have best before dates leading up to and including February 14 and are in all states and territories except for Tasmania and Western Australia.

The health department identified the lettuce after recording an unusually high level of salmonella anatum strain infections and traced a number of those back to the products.

"Normally we only see a handful of cases of this strain each year, but so far this year there have been 28 adult cases of salmonella anatum – mostly adults - notified to the department," the department's senior medical advisor Dr Finn Romanes said.

"As a result of following up the food histories of a number of people we have discovered a common source - the Tripod Farmers lettuce.

"Tests of three products from two batches have also tested positive for salmonella anatum bacterium."

Dr Romanes said two of the 28 people affected by the outbreak had been hospitalised, and that the infection could be fatal for people with compromised immune systems, babies and elderly people.

Have you been affected? Email scoop@theage.com.au

Given the prevalence of the products and their distribution through supermarkets, he said the cases known to date were likely to be the "tip of the iceberg".

"We do expect to see more cases," he said.

"We are working with the company to understand what may have occurred... They have instituted a comprehensive clean-up to make sure any risk is minimised."

He said the 28 cases were mostly adults. No pregnant women had been affected so far and no deaths had been linked to the outbreak.

Dr Romanes said the department of health became aware of the link between the outbreak and the bacteria at Tripod Farmers in Bacchus Marsh, in Melbourne's outer-west, on Wednesday. Since then, the department has been working with the company on a recall of affected products.

He said the anatum strain of salmonella was uncommon and could be found in chicken and egg products. He suggested that fertiliser including affected chicken and eggs may have caused the bacteria to spread at the Tripod Farmers market in Bacchus Marsh.

The NSW Department of Primary Industries said there had been no reported cases of salmonella in NSW linked to the recalled products.

The recall is not limited to Coles and Woolworths and will affect other grocers and businesses.

Diet-food delivery service Lite n' Easy has told its customers not to eat the salad component in its pre-made lunches and to seek medical attention if they had eaten them and felt unwell.

Lite n' Easy said it was replacing Tripod Farmers as its lettuce supplier.

Tripod Farmers is issuing a national recall of the products and anyone who has them at home should either throw them out or return them to the place of purchase.

Dr Romanes said if people were unwell and concerned they should see their doctor and get a simple test for salmonella.

Brenda Williamson said she fell sick after eating a supermarket salad mix three weeks ago.

"When I ate it, it had a bit of a strange taste, a bit soggy and a bit sour... within six hours or so I was having massive cramps and diarrhoea, headaches and nausea for three days flat out - I lost five kilos and I'm only a tiny person," she said.

"I didn't know lettuce could have that effect – I have half a bag which will be thrown out," she said.

Ms Williamson, who lives in Melbourne's south east, said won't be buying packaged lettuce or salad again.

The Food Standards Authority of Australia and New Zealand has issued a recall notice on its website.

Products recalled:

Woolworths is recalling five products in NSW, Victoria and the ACT with use by dates of February 14 or earlier.

Coles said it was recalling the following pre-packed bags of salad in NSW, Victoria, ACT, Northern Territory and South Australia with use by dates of or before February 11.

Coles said pre-packed lettuce with a use-by date of February 12 or later was safe to eat.

On its website, Tripod Farmers say they are "considered Australia's leading salad company" farming over 2000 acres across Western Melbourne, Gippsland and the Sunraysia regions.

The company says it supplies lettuce leaves and gourmet mixes to large and independent supermarkets across Australia and overseas, as well as to domestic wholesales markets in Melbourne, Sydney, Brisbane and Adelaide.

- with Patrick Hatch

BusinessDay, Sydney Morning Herald