Salisbury District Hospital has this morning asked people not to attend unless they are acutely ill or in need of urgent treatment.
The statement from Salisbury NHS Foundation Trust said the hospital is under enormous pressure and it is taking the measures to allow staff to care for patients with severe or life-threatening injuries and illness.
It asks the public to consider alternatives for treatment for minor injuries or illness such as the Salisbury Walk-In Centre in Avon Approach, local pharmacists or calling NHS 111.
The announcement follows a closure to all but essential visitors that came into effect from midnight on January 1 this year.
The measures were implemented in response to the growing number of COVID-19 infections in the local community, with a few exceptions, such as those visiting patients receiving End of Life care, the maternity ward and those visiting children.
Also in January, Great Western Hospitals NHS Foundation Trust in Swindon declared a critical incident as it faced increasing pressure from the Omicron variant of Coronavirus.