Visiting has been suspended at Crosshouse and Ayr hospitals, it has been announced this afternoon.
NHS bosses cited the rising Covid-19 cases as the reason behind the "difficult decision".
Only essential visits will be permitted at Ayrshire's two biggest hospitals with immediate effect.
All other hospitals will continue to support two designated visitors, officials confirmed.
Jennifer Wilson, interim nurse director, explains: “As community prevalence of Covid-19 continues to rise, we are seeing increasing numbers in our acute hospitals, University Ayr and Crosshouse.
"In order to limit the spread and maintain the safety of all our patients and staff, we have had to make the difficult decision to suspend visiting in these hospitals.
"Please be assured that we will be carefully monitoring the situation and will look forward to welcoming back visitors when it is safe to do so.
"We know this will be difficult for our patients and their families and ask for your co-operation to keep everyone safe.”
NHS Ayrshire & Arran say that ward staff continue to support patients and their loved ones in touch during this time with the use of technology.
Anyone that would like to arrange a 'virtual visit' (video call) with a friend or family member in hospital can contact the ward directly to organise a call.
All wards have iPads/iPods specially set up to enable 'virtual visits' (video call) allowing patients to see and talk to the people who matter to them using Zoom.
Anyone with a visiting appointment arranged at either of the affected hospitals, should not attend as all appointments have been cancelled with immediate effect.
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