Buildings which were forced to close by the government because of coronavirus could have an increase risk of potentially fatal Legionella.
On Sefton Council's website it said due to buildings being ordered to shut there is an increased risk of the bacteria forming if action is not taken by people in charge of the property.
Therefore, to minimise the risk of the Legionella, hot and cold-water systems should be used at least once a week to reduce this risk.
On its website Sefton Council said: "As buildings are closed during COVID-19, there is an increased Legionella risk if action is not taken.
"As a general principle, outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow and to minimise the chances of stagnation."
In a published letter from Public Health England, it said people in charge of empty buildings should set up a "flushing regime" or other ways in order to reduce stagnate water forming.
The letter from Public Health England said: "To manage the risks during non-occupancy, consideration should be given to implementing a suitable flushing regime or other measures such as draining the system if it is to remain vacant for long periods.
"This guidance also applies to workplaces which become less occupied (such as outpatient wards)."
Legionella is a bacteria which can cause Legionnaires' disease, a lung infection which is caused by inhaling droplets of water from things like air conditioning or hot tub.
Although the disease is rare, according to the NHS it can be very serious and it's usually caught in places like hotels, hospitals or offices where the bacteria have got into the water supply.
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It is rare to catch it at home.
The disease can cause a potentially fatal form of pneumonia and symptoms include a high temperature, feverishness, cough, muscle pains, headache, diarrhoea and mental confusion.
You cannot get the disease from drinking water, other people with the infection and places like ponds, rivers and rivers.