There was no real great influenza. However, millions of people did die from starvation and other diseases after World War II. Here is my response to that:

After hostilities in Europe ended in the spring of 1945, there was wide spread famine in Central and Eastern Europe. All of the displaced Holocaust internees and Axis held POW survivors were released to go home. The problem for many of these people was that their home was now in a new country, after borders were re-drawn in Potsdam Conference. Another problem for these displaced people was the distance. How on earth could someone who was in a camp in Germany get back to eastern Ukraine? Lastly, another huge problem for many of the displaced persons was even though they were held in camps and prisons by the Axis powers, that didn't nesiscarily mean that they would be in the good graces of their home country's new government. Most of Eastern and Central Europe was now Communist. Many former POWs, such as Poles, were not welcome in the new communist countries, because they were seen as nationalistic. Many of the internees, former POWs, and Holocaust survivors from the Soviet Union faced potential deportation to Gulags, with Soviet officials stating that they were exposed to capitalistic and fascist ideals - even if they were in horrid conditions in POW and Concentration Camps. Many Holocaust survivors and Soviet Soldiers that were in German POW camps were now deemed as potential enemies of the state, and were sent to Gulags for many years.

This doesn't even include repatriated Axis soldiers (not just Germans, but almost every nation in Europe had soldiers fighting for the Axis cause, either directly in German units or under their own country's Armies such as Romanian, Hungarian, Italian etc...). Many could not go back to their native countries because they fought for the Nazis. Foreign Waffen SS volunteers were especially hated. Many French, Dutch, Belgian, and Scandinavian Waffen SS volunteers refused to return to their home countries after being released from Allied POW camps. They knew they ran the risk of being sent to prison, or killed for being traitors. Many of these people ended up in Germany and Austria, trying to figure out what to do next.

It was even worse for volunteers / conscripts formerly from Soviet countries. These people, especially Ukrainians, and various Russian ethnic minorities had been in the Red Army, were captured in 1941 by the Germans, defected to the Germans or were conscripted. They served all over Europe either in their own units overseen by Germans or as 'Hiwis' (Hilfswillige = Willing Help, aka Volunteers) working in German Wehrmacht units. These guys mostly fought in Western and Southern Europe, because the Germans feared they would defect again if the Soviets welcomed them back - which the Soviets did not. These Hiwis were absolutely hated by the Soviets. So many tried surrendering to the Americans, British, French and Polish. However, per the Potsdam Conference, all Eastern European, particularly former Soviet citizens had to be repatriated back to the Soviets. This handed the vast majority of them a death sentence. The majority of officers were killed, and the enlisted men were severely beaten, had their citizenship taken away, and were sent to Gulags where they remained.

Former German soldiers that were deemed "deNazified" were allowed to return to Germany. However, much of Germany was now Polish, or Czech. With East Prussia going to Russia, and large swaths of Prussia, Pomerania, and Silesia going to Poland. Germany's eastern border was now drawn at the Oder. The Soviet Union wanted to keep the territory it had originally taken from Poland in 1939, and was not willing to concede it back to Poland in 1945, but Poland was given reparations by growing its borders westwards and south in to Germany. Not to mention most German soldiers feared the reprisals by Soviets, and did not want to be repatriated back to their former home towns which now fell in to the Soviet occupation / East German zone. So many did what they had to do to avoid going back home.

Now imagine the Red Cross, all of the western Militaries and various other aid organizations trying to help out in this mess. Imagine all of the 18 year old farmers who were either carted off to camps or were now in military, or dead on the battlefield. The tens of millions of mass displaced people, plus lack of farmers, and just an overall destruction of infrastructure and industry all over Europe, made the summer of 1945 and the following winter, some of the worst famine and disease ridden periods of time in Modern European History!

For further reading of death numbers, and diseases etc.. read

"Savage Continent: Europe in the Aftermath of World War II" by Keith Lowe

" After the Reich: The Brutal History of the Allied Occupation", albeit a little biased against Allies

"Bloodlands: Europe Between Hitler and Stalin " by Timothy Snyder. This is a great read for how Eastern and Central Europe were affected by Hitler and Stalin, with a little a bit of the aftermath of the war.

If you're referring to the Great Influenza of 1918, the reason there wasn't one at the end of WWII is the same reason there isn't one in any given year, which is that mutations in the influenza virus are random.

The fact that that flu happened in 1918 was pure chance and had little to do with the war, although the troop ships moving across the Atlantic at the time did have the effect of exposing more soldiers to the virus than otherwise would have.