Hugh Pennington

Eliminating an infectious disease by deliberately eradicating the causative agent has happened only twice: smallpox fell in 1977 and rinderpest – cattle plague – in 2011. Polio should be next, but the murders in the last week of vaccinators in Pakistan – one in Charsadda, two in Peshawar, five in Karachi – have stopped the eradication programme. Nothing new for the Taliban, who blocked polio immunisation in Waziristan earlier this year. Things haven’t been helped by the disclosure that Dr Shakil Afridi, whose activities helped to locate Osama bin Laden in Abottabad, operated under the cover of a bogus immunisation programme run by the CIA.

With two million cases in the UK every year, norovirus exceeds all other causes of diarrhoea and vomiting by many orders of magnitude. If a malevolent person had set out to create it as the nastiest virus known, their only disappointment would be a lethality failure; the vast majority of victims get better after two or three days without specific treatment. Just as well, because there isn’t one.

A coronavirus particle has spikes on its surface with knobs on the ends, making it look a bit like the sun and its corona. Hence the family name. Human ones were first seen in the 1960s by the electron microscopist June Almeida, in collaborative common cold research with the virologist David Tyrrell. Growing the viruses was very difficult. Almeida and Tyrell were enthusiasts for organ culture (I am reminded of it daily; I worked with June and have a scar on my forearm where skin was taken in a vain attempt to grow wart viruses). Bits of tissue kept alive in test tubes were infected with sneezings from common cold sufferers. It turned out that a quarter of colds are caused by coronaviruses.

Legionnaire's disease got its name in a blaze of publicity when attendees at the 1976 Philadelphia State Convention of the American Legion were struck down with severe pneumonia. They had stayed at the Bellevue-Stratford Hotel from 21 to 24 June: 182 fell ill and 29 died; 39 passers-by were also affected, five fatally. Funerals and marching legionnaires made good television. The story was top of the news for five nights. But the cause was a mystery until a cold review of samples from victims was conducted six months later. It turned out to be a bacterium. This was unexpected. The pathology didn’t fit a bacterial cause, and it was widely believed that bacteria did not spread on the wind.

The influenza season draws to a close. But the virus isn’t going quietly. Monday 2 April started early for me with an interview on the Today programme about the sensible decision by the US National Science Advisory Board for Biosecurity to give up trying to censor papers describing the enhancement of bird flu infectivity in ferrets. I covered the same story for Good Morning Scotland. The benefits of knowing about potentially nasty mutations before they take us by surprise far outweigh any risks from al-Qaida virologists.