Well lets not frighten Gardeners, there are quite a few issues with various diseases that you can get from potting down the bottom of the Garden...

Legionellosis (Legionella): caused by Legionella bacteria, this is an infectious disease that can be caught by anyone, but elderly gardeners and those with a suppressed immune system are most vulnerable. There are two types to which gardeners may be exposed: Legionella longbeachae, occuring in soil and compost, which can lead to a respiratory disease; and the more common L. pneumonophila, which leads to a type of pneumonia known as legionnaires disease. The latter form occurs naturally at low levels in watercourses but can multiply in standing water to potentially harmful levels when the water temperature is between 20°C to 45°C.

Bioaerosols: these are airborne micro-organisms including spores, bacteria and fungi (e.g. Aspergillus fumigatus) that are naturally present in decomposing material. Gardeners are most likely to breathe these in when turning compost, especially in warm weather. People with an existing chest conditions such as asthma or bronchitis or those prone to allergies are most at risk.

Tetanus: the tetanus bacterium can enter through cuts or wounds. Since gardeners regularly handle thorny plants, soil or manure, they are at a higher risk of being infected than non-gardeners.

Weil’s disease (Leptospirosis): this is a disease humans can catch from rats through water or wet vegetation contaminated with rat urine. Rats also transmit salmonella.

what can you do to minimise the risks i've put a few ideas here so you can write up your own assessment

Wear gloves whenever handling soil, compost, fertiliser or pesticides. Thin latex (or latex-free for allergy sufferers) gloves can be worn for delicate work.

Do not open bags of compost or potting media with your head right over it.

Fold over the top of compost bags when not in use.

Avoid potting-up in confined spaces.

Moisten dry potting media before use. Also dampen down dry compost heaps before turning or use.

Consider wearing a dust mask when turning compost heaps and handling potting media or other dusty materials.

Avoiding storing potting media in greenhouses as these will heat up and may encourage Legionella.

Empty the water out of garden hoses after use and do not leave full hoses in the sun after use.

Avoid splashing water around when watering pots.

Keep water storage containers such as tanks and butts clean by emptying and scrubbing out once a year. Insulate them to reduce temperatures increasing in warm weather or paint them with a light colour to reflect the heat.

If the temperature of stored water for use in mist irrigation or sprinklers is above 20°C, do not use.

Wear gloves and keep arms covered when pruning plants that can cause irritations; e.g. ivy (Hedera), Fremontodendron, Euphorbia or rue (Ruta).

Only shred woody prunings in an open, well-ventilated area.

Ensure tetanus jabs are up to date. Otherwise, see your local GP for a tetanus vaccination if you have cut yourself on a plant or got soil or manure in an open wound.

Discourage rats by securing rubbish in bins and not putting cooked food on the compost heap.

Rat-proof compost bins with wire mesh if necessary. To reduce the risks from salmonella avoid using rat-infested compost on edible crops, especially those not cooked before consumption.

Protect from water-borne diseases such as Weil’s disease by wearing waterproof gloves, clothing and boots when clearing out ponds.

Always wash your hands after gardening and especially before eating.

Keep a hand sterilising gel down in the potting shed if clean water is not available.

A lot of it is common sense and there has been generations of gardeners that have never had any issues or medical problems by simply following simple hygiene practices

Common sense prevails, never heard of gardeners dying in the news lately, Just good old common and wash your hands before you eat or smoke

There is a link - as seen in the Scotland news article. It seems most likely that it arises from moist compost being aerosolised.

Longbeachae was the causative organism in those cases.

There is a dose-exposure curve for legionella even if no-one knows what it is exactly. So minimise exposure sensibly - working inside small hot greenhouses and opening multiple bags of compost with your head in close proximity to the contents will probably increase your risk. Working outside and keeping your head out of the bags will help to reduce your exposure.
At this stage, unless they're a vulnerable person in regards legionella, I'd struggle to recommend doing more.