London

An airtanker arrives, every day, to dump white powder over the city. The drops focus on Hyde Park, ground zero for the infection. 25 tons of powder per day adds up, blowing about the city and piling into drifts. When it rains the mixture foams and bubbles, and bleaches the stone as it drains towards the Thames. The river is as dead as the city, but with the population of Great Britain dead or evacuated, no one complains. Nature has grown strong enough and weird enough to look after itself anyway.