The American Red Cross has declared the second-ever national blood supply crisis after blood donations fell to a four-year summer low.

On Monday, the 145-year old non-profit said that as the United States’ largest single provider of blood products, it now has less than one-day national supply of type O positive blood – the most commonly transfused blood.

Type O positive blood accounts for about 60% of the ARC’s blood distributions and is used across everyday patient care as well as medical emergencies. It can be given to about 80% of patients, according to the ARC.

“Despite thousands of people answering the call to give, blood donations are not keeping pace with hospital demand – which is up during the summer trauma season. Extreme heat, poor air quality and widespread foodborne illnesses are contributing to lower donor turnout this summer, further straining the nation’s blood supply,” the ARC said, appearing to refer to the cyclosporiasis outbreak that is suspected to have affected more than 11,500 people across the US.

Just three additional donors at each blood drive this summer can end the crisis and stabilize the blood supply, according to the ARC, which also stressed the need for a strong supply of every blood type.

“When hospitals have adequate supplies of A, B and AB blood, they can provide patients with blood that matches their blood type whenever possible. This preserves type O blood for patients with type O blood and for life-threatening emergencies, when there isn’t time to determine a patient’s blood type,” it said.

This summer’s crisis follows the first national blood crisis in 2022, which was driven largely by the Covid-19 pandemic as well as extreme weather events.

The ARC is not the only organization raising concerns over the nation’s blood supply shortage.

Earlier this month, the Association for the Advancement of Blood & Biotherapies Interorganizational Task Force on Domestic Disasters and Acts of Terrorism said the US blood supply is “significantly lower than it should be”.

Earlier this month, both the Connecticut Blood Center and the non-profit blood services provider Vitalant also declared emergencies on blood supply shortages.

Approximately 62% of the US population, roughly 212 million people, is eligible to donate blood, according to America’s Blood Centers. However, only 3% donate each year.