Joe Biden’s great-great-great-grandfather, Edward Blewitt, was overseer at the Ballina Union Workhouse in County Mayo from 1848 to 1850 during the Great Irish Famine. Many died in the workhouse and others perished in the temporary fever hospital built against one of its walls. With his family, Blewitt emigrated to Pennsylvania in 1851. He did well, despite the political power of the anti-Catholic, anti-Irish Know Nothing movement, a nationalist and Protestant political party, which in the 1850s had a hundred congressmen, eight state governors, and a controlling position in half-a-dozen state legislatures. Before his job at the workhouse, Blewitt had been an engineer for the Irish Ordnance Survey; in Pennsylvania he helped to lay out the new mining town of Scranton.

More than sixty years ago, puffing on an untipped Senior Service (we were allowed to smoke in those days) to cover up the reek in a dissecting room at St Thomas’s Hospital, I was struck down by a pandemic virus that had recently evolved in China. By the time I fell ill (its onset was very sudden) the virus had already killed more than 20,000 people in the UK, with 1150 dying every week at its peak, and 80,000 in the US. In the first UK wave, more than half the deaths occurred in the under-55s. It went for the elderly later, in its second wave. It killed quickly: nearly 20 per cent of its younger victims died before getting to hospital and two-thirds were dead within 48 hours of admission. But it has been airbrushed out of history, despite being by far the most lethal pandemic to affect Britain at any time in the hundred years after the ‘Spanish’ flu pandemic at the end of the First World War.

Health officials in Kerala have confirmed a number of deaths from Nipah virus in the south Indian state. In the Democratic Republic of Congo, there is an outbreak of Ebola. Earlier this year, a team of virologists, bacteriologists and infectious disease experts met at the World Health Organisation’s headquarters in Geneva to determine which diseases and pathogens pose the greatest public health risk because of their epidemic potential and an absence of effective drugs and vaccines for treatment and prevention. Both Nipah and Ebola are on the list. The 2018 Research and Development Blueprint, released in March, also includes Zika virus, Lassa fever (a viral haemorrhagic disease occurring primarily in West Africa), MERS-CoV and Sars – and something called Disease X.

The first death caused by swine flu virus outside the Americas occurred in Scotland on Sunday. The announcement generated more media interest than the declaration three days before by the World Health Organisation that the spread of the virus had moved into pandemic mode. But the declaration was expected and generated less fear than anticipated. The public can see that in Britain the virus is doing well – which is all that was needed to meet the pandemic criterion of sustained community spread in a region outside the Americas – and the message that the virus is mild is also well established, tempering the notion that the word 'pandemic' carries lethal overtones. But this means that a death requires explanation. There is no such thing as a naturally avirulent influenza virus. Even the mildest ones that infect humans can kill. They do it routinely every winter.

The spread of the novel influenza A(H1N1) virus through North America is nearly complete. Only three continental US jurisdictions (Wyoming, West Virginia and Alaska) and three Canadian provinces or territories (Newfoundland, Nunavut and the Northwest Territories) haven't reported cases. Its progress elsewhere is still slow, however. Japan (163 cases), Spain (103), the UK (102) and Panama (54) lead; vigorous containment is still the order of the day in the UK. But unless the North American epidemic slows soon, the continued export of the virus – in the coughs and sneezes of infected travellers returning home (particularly to the southern hemisphere, which is just entering its flu season) – has a good chance of defeating all best-laid plans. And it is doing well in Japan.

Influenza virus has only eight genes. The molecular structure of the most important proteins they code for is known in intimate detail. The coming and going of its epidemics have been studied by statisticians continually since the 1840s. But predicting pandemics remains a fools’ game. It falls into the category of Alvin Weinberg's 'trans-science' – a question of fact that can be stated in the language of science but is unanswerable by it. Weinberg’s examples focused on the impossibility of predicting the probability of extremely improbable events. There have only been three influenza pandemics in the last century: in 1918, 1957 and 1964. The uncertainty is massively amplified by evolution – the random and frequent genetic mutations and the swapping of genes between bird, pig and human viruses.