Please, read the spoilers by clicking them.
September 30, 1944. Following Germany's slow victory over Polish Underground Movement partisans, Germany wanted to turn Warsaw into ruins. However, the Polish partisans had something, a strange substance that neither side knew about, because if either Allies, Axis or Comintern (Comintern was Russia) knew about the substance, their sovereignty would be over. Despite all the attempts to research it, the Poles never understood its power, and when October loomed, they surrendered to the Germans. However, the destruction of Warsaw had far more consequences. By doing this, Germany accidentally destroyed the container of substance, the Polish were trying to research, and it, as well as an event 74 years later, would have far-reaching consequences not just in Poland, but across the entire Earth.
After Soviets recaptured Warsaw, the first known occurrence of a change happened, but it was cleverly hidden as "AKs guerrilla warfare." Apparently, there were makeshift defence measures against the substance, which leaked after destruction of Warsaw, such as walling off the sewers. Proper ones were made when World War II has ended, like restoring Warsaw, the communist government and the Palace of Culture and Science. Every citizen that had been changed was taken under 'casualties', and then killed off. This contained the disease somehow, but not for too long.
Year 2018. Nothing unusual or odd from what you, people, call Earth. Life there is like heaven, with the only disturbances being the wars in Ukraine or the Civil War in Syria. Most people have gotten lazy, and some of them brainwashed by industries, some of them corrupted. Elsewhere, starving children can be fed by richer countries. This might not be obvious at this point, but something darker and unusual looms beyond humanity. Something linked to the past, that will change everyone in the future.
May 26, 2018. This day was the day where a maintenance of the sewer system was commenced, but not everything went as planned when the strange 'virus', as some cynic was describing the substance, was released. It spread over Warsaw and then over the world by the war. Poles neglected this somehow, mostly because of lack of knowledge, as most of the notes were in Soviet archives, and would be hidden until January 2045 at earliest.
June 1, 2018, 13:00. In Warsaw, Poland, life was normal. Sometimes people were protesting against the government. Corporate skyscrapers were rising from ground, and the Palace of Culture and Science was being landmark of this city since the 1960s. The city itself didn't vary much from other modern cities.
Suddenly in the Old City district, a couple living happily the in civilian complex got sick. Worried about their state, their son called for an ambulance. Five minutes later, paramedics arrived in location, where supposedly the couple was, but the son had fallen ill, too. The ambulance took them all to the hospital, where suddenly, all three began to develop various animal traits. The youngest, Marcin, gained black fur, and the ears spiked out, while limbs suddenly began to change their position. He himself had begun to shrinking in size. The mother of Marcin, Anna, developed wings. On closer inspection, she also developed black pitch scales, and her green eyes began to give a faint glow. She was becoming bigger, too. The oldest, husband of Anna, Adam, fainted instantly, and his body shrunk to the size of five-year old human before... surprise, he developed some sort of appendages, along with blue, black and beige fur. Polish doctors, confused, left the room instantly.
But neither of the original three who changed survived the fire shortly after. The criminal, a doctor, was arrested for arson, murder and destroying public inventory. On his trial, he admitted to the crimes due to "hatred to animals". Confused, the judge looked at the bones. They resembled not humans... but something else. Something that they didn't know. Something, that they didn't suspect, yet clearly was a sign of the past. From this point, Earth passed the point of no return.
July 21, 2018. Poles were once more fighting, but not just for independence. This war was over influence over Poland between America, Poland and Russia, disguised as 'terrorists took over Poland', and rights over research of what really happened there. Lives were lost, although not as much as in the 1939 aggression of Germany against Poland. People couldn't put up a successful resistance, because of the betrayal and the fact that most of the troops weren't mobilized yet.
July 24, 2018. Poland stood no chance against NATO and CSTO combined forces and capitulated. These two factions, not wanting to escalate war, partitioned Poland between two occupation spheres, despite protests of most members of UN, and even North Korean leader, Kim Jong Un, deeply felt sorry for what happened to Polish people. The war was otherwise known as Three Days War. Then, some towns - Gdańsk, Kraków and Kielce were released as independent free cities.
However, today, July 26, 2018 will stand as Hour 0. Most of the time you heard about turned people from local radio or television channels. While corporations are trying to profit from these news, you might shortly change into non-human creature. You can feel it, albeit it's too faint to clearly feel it. You can hear it coming, yet it's too silent to catch this sound from many others. But when will it strike and where? If it came, who will you be? Or... what will you become? Will you adapt, perhaps even killing anyone who stands in your way, or die to more or less usual causes.
The main news source is the Free City of Kraków. This city was unaffected by the war, however it's governed by the UN to ensure no further wars will break out, like uprisings or war for influence. Lately, there were a lot incidents of people there getting turned into creatures, of varying shapes, sometimes resembling our video game creatures, like Pokemon. Wawel castle, located in this city, was a place where peace treaty to end the Three Days War was signed.
However, starting location is in Barcelona, Spain. This major city in Spain is attractive for tourists. Some of people there were drawn into the war against Poland. Due to a touristic boom after the war, to ensure the illusion, most tourists are actually from the EU, including their former member, Poland, and the USA. It's extremely possible that the new outbreak will start in Barcelona. If not by air, some refugees might start it.
The city itself is on the brink of revolution, as you can see the Catalans protesting every day against Spain's policies. It looks like shown in spoilers:
You, as a citizen of Barcelona or perhaps - a tourist/refugee who happened to be there, are the one of possibly many humans to find out the hard way... that sooner or later, you will turn. Although you're a human for now, some people with known case of paranoia, would point out that everyone is the Morph, or Warsawian, as to refer to the first three people who changed. They would also claim you were replaced by an alien or something equally hostile. Although you and most people there don't suspect anything, the change might be enough to shatter the calmness of people.
The Changed are somewhat more everyday news, as they don't have set species or even type! Some of them might turn into our familiar animals. Some may turn into creatures of myths, like dragons. Even transformation into something called Pokemon was possible by that. Some species though don't resemble any kind of source searchable normally on the Internet. Sometimes they are called abominations, monsters or animals, depending on traits and comparing them to animal. The only problem is - they have high mortality rates due to them being threatened both with natural causes, as well as the urban ones like cars, paranoid humans, criminals, sometimes even related to their species. Thankfully, despite that, some people might still protect Changed, and law is still enforced so turned people are theoretically safe, although the creatures that were once humans wouldn't be comfortable with that.
However, don't let your guard down. If you get too careless in the city and show in it too much, you might find yourself in so called quarantine and pack more of city into problems. These problems are for example - police time between 11:00 PM and 6:00 AM or bullying innocents to get them into lab in hope to get a cure, that just won't happen at all. Police might also check for any trace of you and try to relocate you into wild. On other side, the law might collapse instead and the only ones who could protect you are either yourselves or kind people.
You can try to live as it nothing happened. But it isn't simply possible. You can run away and start the life anew, or stay in the city and do the same thing. You can try to find out the answer why you were changed, but that's not going to return you to human form. You can even run rampant, having been enraged by it, but if you're too weak, don't expect the random outrage to be successful. Not even if you're strong. Granted, you'll make some damage, but you'll really drop like a fly after army intervention. But mostly important, you have to adapt to your new body. The cement jungle of Barcelona won't be that safe for creatures as it is for humans. Going outside the city? Might be a good idea, but you need to fight out predators and hunger there, if you ever stand in the forest. Sometimes also illegal hunters would try to hunt you.
As about transformations, a little is known about exact details. A man can be knocked unconscious and begin to change, others might wince from pain while turning, even others might be simply painlessly turned. But it's really a lottery, as you may be changed in very different way than the three ways that are portrayed.