The world is facing its largest humanitarian crisis since 1945, according to the United Nations.

“We stand at a critical point in history. Already at the beginning of the year we are facing the largest humanitarian crisis since the creation of the UN,” UN Emergency Relief Coordinator Stephen O’Brien recently told the UN’s Security Council.

While many countries worldwide face food security crises, with large numbers of people hungry and unable to find enough food, only rarely do the conditions meet the munity’s formal criteria for a famine, says the UN.

The UN declares a famineonly when the following measures of mortality, malnutrition and hunger are met: at least 20 percent of households in an area face extreme food shortages with a limited ability to cope; acute malnutrition rates exceed 30 percent; and the death rate exceeds two persons per day per 10,000 persons.

Other factors that may be considered include large-scale displacement, widespread destitution, disease outbreaks and social collapse.

Currently five countries are facing or are at risk of famine—Kenya, Yemen, South Sudan, Nigeria, and Somalia:

In Yemen, 14.1 million people face severe food insecurity because of armed conflict in the country. Continuing fighting, lack of rule of law, poor governance, and under-development are also preventing foreign aid from getting through. As the BBC notes, a naval embargo imposed by the Saudi-led coalition, fighting around the government-controlled port of Aden and air strikes on the rebel-held port of Hudaydah, have severely reduced imports since 2015.

In South Sudan, 4.9 million peopleface severe food insecurity because of armed conflict that borders on genocide. “The famine in the country is man-made. Parties to the conflict are parties to the famine – as are those not intervening to make the violence stop,” said Mr. O’Brien, who called on the South Sudanese authorities to translate their assurances of unconditional access into “action on the ground.”

In Nigeria, theestimated number of affected children is now 450,000, with 14 million people needing humanitarian assistance across the region.The UN predicts Nigerians likely will suffer “catastrophic” famine-like conditions caused by Boko Haram’s Islamic uprising.

In Somalia 2.9 million are facing famine conditions because of armed conflict.According to BBC news reports, people are so busy trying to survive that they are unable to earn a living by going to work, farming or looking after their animals.“The current indicators mirror the tragic picture of 2011, when Somalia last suffered a famine,” said O’Brian, who added that a famine could be averted with “strong national leadership and immediate and concerted support by the munity.”

In Kenya,2.7 million people face severe food insecurity, but it could soon increase to 4 million. The cause of this famine isdrought associated with the ongoing El Nino weather phenomena, but government petence and an inflow of refugees from Ethiopia is preventing relief aid from dealing with the problem.“In collaboration with the Government [of Kenya], the UN will soon launch an appeal of $200 million to provide timely life-saving assistance and protection,” said O’Brian. But he adds that about $1.5 billion is required to provide the assistance needed across the region.