There was consternation mid-August because Dutch sausages and ham were said to have infected thousands of British people with the hepatitis E virus (HEV). The evidence came from a study by Public Health England. What went wrong? ‘It is difficult to prevent these sorts of infections,’ says virologist Wim van der Poel of Wageningen Bioveterinary Research.
How can this virus get into meat?
‘The hepatitis E virus occurs on more than half of our pig farms and roughly 10 percent of the pigs are carrying the virus at the point of slaughter. That is how the virus gets into meat products.’
Can this be prevented?
‘It is difficult to prevent infection: the virus can survive very well in pig populations. You can deactivate the virus in pork and meat products by heating them. That has to be done at a minimum of 70 degrees Celsius and for at least three minutes. The problem is that this is not done enough in the case of various products or by-products of the pork industry. Take raw sausages such as liver sausage, cervelat and dried sausages, for instance.’
British pigs are infected with HEV too. Yet people are rarely infected with that strain. How come?
‘HEV is present on pig farms in Great Britain as well, and people get infected with it there too. There is evidence, though, that the European strain of HEV is found in the blood of British blood donors more often than the British one. But it is not clear why that is.’
How much risk is there from other animal products such as milk?
‘In the Netherlands all cattle are tested for HEV antibodies and so far they are not carrying the virus.’
Can’t we test pigs and produced hepatitis-free meat?
‘HEV-free meat is a pipe dream for the time being. You have to set a realistic target and be able to say exactly what it means in practice. Less of the virus, or no virus at all? It would not be easy to make all the pigs in the Netherlands virus-free. And to then keep farms virus-free through extremely strict hygiene would be extremely difficult. You actually need to vaccinate, but there still isn’t a good vaccine against HEV in animals.’