The American Red Cross has declared a nationwide blood crisis after donations fell to their lowest summer level in four years, worsening shortages for hospitals and patients. The organisation says the situation could threaten access to lifesaving transfusions, with type O blood supplies of particular concern.

The warning is described as only the second blood-supply crisis declared by the Red Cross. It is urging eligible people to donate, as blood is needed for emergency treatment, surgery, cancer care and other medical conditions across the United States.