Enterovirus D68 - how worried should we be?
Remember necrotising fasciitis, the 'flesh-eating bug'? A few years ago, there were wall-to-wall headlines about the risks of this infection, which kills up to three people who get it. Yet when we looked at the statistics, it turned out there was little change in the number of people actually catching it. The difference was that the media had cottoned on.
This month there's a new kid on the block - the enterovirus D68. It comes from a family of viruses (the enteroviruses), so-called because they're passed on through the intestine. They tend to be lumped together into polio and non-polio enteroviruses - and D68 falls into the latter group.
Between them, the 100+ non-polio enteroviruses cause up to 15 million infections a year - mostly mild colds. They include the cocksackie virus, which causes hand, foot and mouth disease. Three echoviruses in the group (13, 18 and 30) have caused outbreaks of meningitis in the USA.
But in 2014, enterovirus D68, which had first been identified in California in 1962, gained notoriety when it caused a spate of severe respiratory infections (at least 1,153 were confirmed in 49 states), some cases of paralysis and was linked with 14 deaths. Severe complications were almost all confined to children, with asthma sufferers most vulnerable of all.
Thus far, there seem to be no more cases of enterovirus D68 in the USA than usual this year. By contrast, in the UK, this year seems to be a worryingly troublesome year for the virus. In 2012 there were seven cases confirmed; in 2013, three cases; in 2014, 56 cases; and in 2015, 14 cases. So far this year, the UK has seen 38 confirmed cases.
Most cases cause mild cold-like symptoms, including runny nose, coughing and sneezing. It can cause much more severe breathing difficulties. In rare cases, it can lead to sudden severe limb weakness and even paralysis.
Enterovirus D68 is probably spread by droplets in the air when someone sneezes or coughs, or by touching a surface the droplets have landed on. Covering your mouth when you cough or sneeze, using disposable tissues (just once please!) and washing your hands after sneezing or coughing can help reduce spread. Cleaning surfaces including door handles regularly will also help. However, it can also be passed on through the gut, so hand-washing after using the toilet and before touching food is essential to reduce the risk of passing it on.
Because enterovirus D68 usually causes only mild, short-lived symptoms, it's likely that the real number of cases is very much higher. It's possible that the increase in UK cases between 2013 and 2014 arose not because there was more virus around, but because the American outbreak meant patients with chest problems were more likely to be tested for it.
In the USA, infection with enterovirus D68 seems to be most common in summer and autumn, while in the UK spring and summer seem peak seasons.
However, there has been enough concern for Public Health England to issue a warning to doctors to be on the look-out for enterovirus D68 in children with severe breathing problems or muscle weakness. Thus far, they estimate that:
- The likelihood that any single case of sudden paralysis is down to the virus is very low
- The chance of a cluster of cases of severe breathing problems is low
- There is a moderate chance that the virus is circulating in the population largely undetected.
Enteroviruses include the polio virus, which before the introduction of immunisation in 1955 caused 4,000 proven infections a year in the UK, many of them leading to paralysis or death. Fortunately, polio immunisation means there is a real chance the world will be free from polio - the World Health Organization declared the USA polio free in 1994, with Europe following in 2002.
The current aim is for a last push to clear the world of polio by 2019. Only when it's gone everywhere can we relax - in 2011, polio from Pakistan spread across to China, which hadn't seen a case for a decade. As of today, only Pakistan and Afghanistan remain to be declared polio free.
At present, there is no vaccine and no cure for enterovirus D68. Of course every severe case is devastating, the risk of paralysis is much lower than with polio, and the number of confirmed cases even this year is way below the 4,000 cases of polio seen every year before immunisation. Should we be cautious? Definitely. Terrified that the new polio is upon us? Almost certainly not.