We argue that the new coronavirus COVID-19 was probably linked to the arrival of a pure culture of the virus in cometary debris that was deposited in the stratosphere, and first came down in the Hubei province of China. The subsequent worldwide spread of the virus has taken place by a combination of two effects: the deposition of further large quantities of virus at several locations – Iran, North Italy, South Korea – combined with much slower spread through person-to-person infection (itself largely by contaminated surfaces and personal affects). The location of the foci outside China all lie close to latitude 40 degrees N, consistent with the transport of aerosols by cyclonic winds in the stratosphere. It is also remarkably consistent with observations in the 1960’s of the fall-out of radioactive dust deposited in the stratosphere in the last of the atmospheric atom bomb tests. On this basis, we conclude that a stratospheric loading of the Coronavirus that happened in October/November 2019 could take a few winter seasons to be fully drained. A clearer understanding of the causal events that led to the COVID-19 pandemic could help planning future strategy.