Trade wars, Middle East turmoil and now the coronavirus – seemingly nothing is capable of dislodging America’s long bull market, now in its twelfth year. There’s no stopping it, with the S&P 500 reaching another all-time peak last week, apparently oblivious to the global health scare.

The virus may be a bigger phenomenon than markets assume, or indeed the Chinese authorities are prepared to admit. Both the numbers affected and the mortality rate are almost certainly higher than official numbers suggest, nevermind the already manifest economic effects in curtailed travel, interrupted supply chains, a fast-stalling Chinese economy and so on.

If things worsen, it might also pose a threat to the legitimacy of the Chinese high command which, as is the way with authoritarian regimes, has been less than open with the truth. There is no reason to think the incumbency is in imminent danger, but with trouble in the periphery of Hong Kong, Taiwan and the Uighur population of the North West, its position may not be as unassailable as it thinks.

That might of course be a cause for some celebration in the White House. But Trump should be careful what he wishes for. If China begins to splinter, the consequent instability would not necessarily be positive for the West. In any case, in stock market terms the latest pandemic is what Donald Rumsfeld would have called a “known unknown”. The consequences may be big, they may be small, but for now we simply don’t know.