Plague Land Series by Alex Scarrow

Leon and his younger sister, Grace, have recently moved to London from New York and are struggling to settle into their new school when rumours of an unidentified virus in Africa begin to fill the news. Within a week the virus hits London. The siblings witness people turning to liquid before their eyes, and they run for their lives. A month after touching Earth's atmosphere, the virus has assimilated the world's biomass.

They thought the plague was dead. They were wrong.Two years ago, a virus hit London, killing thousands of people and driving the rest into hiding. But Leon has somehow survived, making it through two harsh winters. Now he's living on the fragile hope that the freezing snow and ice of the English climate wiped out the virus for good. Word even reaches Leon of a rescue boat on its way.But all is not as safe as it seems. The virus has been busy...

In one week, the plague destroyed and wreaked havoc upon the world. The survivors thought it was over, but it was only the beginning...Three survivors made it through with just each other to rely on, but now they are scattered across the globe. Leon is in England, Grace is on the way to New Zealand, and Freya to the "New United States."Until now, they and some others were lucky enough to stay alive... moreIn one week, the plague destroyed and wreaked havoc upon the world. The survivors thought it was over, but it was only the beginning...Three survivors made it through with just each other to rely on, but now they are scattered across the globe. Leon is in England, Grace is on the way to New Zealand, and Freya to the "New United States."Until now, they and some others were lucky enough to stay alive. But, when the deadliest and most sinister attack is yet to come, what hope does humanity have to survive? less