The panic over polio has gone global – but is it as frightening as it seems?
As New York declares a state of emergency after just one case...
THE headlines were alarming: ‘Urgent investigations after rare virus detected’ is just one example. Another simply read: ‘Polio horror.’ In late June, health officials announced they had picked up poliovirus during routine checks of London sewage water. Analysis suggested the highly contagious bug, which can cause paralysis and lifelong disability, was silently circulating.
Polio, which primarily harms young children, had not been seen in Ireland since 1984, following one of the most successful worldwide vaccination campaigns in history.
But now it turns out the polio problem is also worldwide. In fact, the situation appears to be worse elsewhere. In July, an unvaccinated New York man in his 20s was diagnosed with polio paralysis. Officials have since discovered the virus in sewage there, and last week governor Kathy Hochul announced a state of emergency.
A similar picture has been seen in Jerusalem, where the first victim of polio paralysis was a threeyear-old girl.
Experts are still unsure what exactly is triggering the return of the virus, but there are already several theories. Many scientists believe that, after decades of successful take-up of the polio vaccine, an increasing number of families are turning down the chance to get their children jabbed, leaving them exposed to infection.
Some also say the uptick may have been caused by global political upheaval, with refugees bringing the virus with them.
Others think that the disease’s comeback is a knock-on effect of another vaccine campaign — the whooping cough jab — which may be blunting the effectiveness of the polio vaccines.
But perhaps most intriguingly, a growing number of experts believe that polio may have been with us all along. The difference now is that we are looking for it. So who is correct? And, crucially, just how worried should we be?
Despite its reputation, poliovirus is harmless to most people. Only one in 200 people who are infected will experience symptoms.
What makes the disease so dangerous is how contagious it is. Studies suggest that for every person who catches polio, six more will become infected as a result.
It is usually passed through contact with the faeces of an infected person. Experts say this means the primary source of transmission is children.
‘Kids are prone to not washing their hands after going to the toilet, so the disease can easily spread between children who then bring it home to their family,’ says Professor Kathleen O’Reilly, a polio expert at the London School of Hygiene and Tropical Medicine.
For the unlucky few who do fall ill with polio, the symptoms can be devastating. The virus can attack the spinal cord and the brain stem, the area that controls muscles and movement.
When this occurs, the condition is known as poliomyelitis, and it can lead to paralysis and death. Patients who survive will often be permanently disabled, losing the ability to use their legs, arms or even breathe freely, due to wasting of the muscles around the lungs. These severe symptoms are most common in children under five.
The first polio epidemic occurred in 1942 and continued into the following year. In all, 487 cases and 133 deaths were notified to the Department of Health, a fatality rate of 27.3 per cent. There were also epidemic waves in 1947, 1950 and 1953.
Those infected during the epidemic included pop star Ian Dury, who was left with paralysis in his left leg, shoulder and arm after catching the virus aged seven. Other memorable images of the era include children undergoing polio treatment in an ‘iron lung’ — a metal chamber which helped to pump the lungs.
Later in the 1950s, hope arrived in the form of a polio vaccine. Created by Albert Sabin, a PolishAmerican microbiologist, it was a
liquid that could be given by mouth — often, it was dropped on a sugar cube. This made it the ideal candidate for mass vaccination campaigns, and a global effort to eradicate the disease was a near-total success.
The last recorded case in Ireland was in 1984, and the virus in its original form is now found only in remote parts of Afghanistan and Pakistan.
But Sabin’s vaccine had unintended consequences. It contains a live polio virus that is weakened using special processes in a lab so it is less of a threat. However, in extremely rare cases, the virus in the vaccine can wake up.
Roughly three in every million people given the oral vaccine developed paralysis — a condition that would eventually become known as vaccine-derived polio. The virus can also infect without causing symptoms, and then be passed on.
For this reason many countries switched to an inactivated polio vaccine — using a dead virus — about 20 years ago.
Some developing nations, including Afghanistan, Pakistan and parts of Africa, still use the old-style vaccine. As a result, vaccine-derived polio does still occur in those countries. According to the World Health Organisation (WHO), there are just under 1,000 of these cases every year, most occurring in Somalia, Sudan, Afghanistan and Pakistan. And it is vaccine-derived poliovirus that has been discovered in the UK.
‘It’s not the first time we’ve found it, but it’s the first time we’ve seen it in such large quantities,’ says Professor Adam Finn, a paediatrician and member of the British government’s vaccine advisory group, the Joint Committee on Vaccination and Immunisation (JCVI).
‘In the past we’ve picked up three or four positive samples a year through routine waste-water surveillance. This year there have been 160 positive samples, so it’s a much more serious scenario.’
Genetic testing of the poliovirus found in London sewage water shows multiple DNA variations, suggesting the virus is not coming from just one person and is being transmitted between people. Experts also say it is possible that previous upticks in vaccine-derived polio may have gone unnoticed.
‘If you’re only looking for a disease once a month, it’s easy to miss cases,’ says Dr Andrew Singer, an expert in waste-water surveillance at the UK Centre for Ecology and Hydrology. ‘That doesn’t mean the virus isn’t there. You just don’t know if it is.’
Experts warn that the more the virus spreads, the more likely it is that cases of paralysis will occur. ‘Given the number of these positive samples, you might have expected to see a paralysis case by now,’ says Prof Finn.
‘This outbreak appears to be self-contained, and there’s really no chance of polio spreading around. But this is a reminder that we cannot afford to allow polio vaccination rates to falter.’
Health officials have been able to trace these samples back to North London, affecting eight boroughs in all, including Camden, Hackney, Brent and Barnet.
‘In some more deprived areas of London, there are a significant number of children who have not had their polio vaccine,’ says Prof Finn. ‘Outside of London, upwards of 95 per cent of children have had their jabs, but in some London boroughs the coverage rates are as low as 75 per cent.’
The polio vaccine is given to all children in Ireland as part of the 6-in-1 vaccine at two, four and six months of age. The 6-in-1 vaccine protects against diphtheria, hepatitis B, Hib (haemophilus influenzae b), pertussis (whooping cough), polio and tetanus. A booster vaccine dose is given at 4-5 years of age (4-in-1 vaccine) which protects against diphtheria, pertussis , polio and tetanus.
Low vaccination rates are a problem in New York and Israel. ‘In the US there is a real problem with vaccine hesitancy,’ says Prof O’Reilly. ‘That’s the reason New York had to declare a state of emergency, because even after they found the polio case and offered more vaccines, no one came forward for them.’
Meanwhile, in Israel, low vaccination rates are a long-standing issue in the ultra-orthodox Haredi Jewish community. The girl infected in Jerusalem was Haredi, and it has been reported that the New York polio case is a Haredi man who had travelled from Israel.
Experts say cases in the UK may also be imported. One country that has been highlighted as a possible source is Afghanistan.
Professor Paul Hunter, an infectious disease expert at the University of East Anglia, says: ‘It’s possible that refugees unknowingly brought the virus with them and it’s now spreading in a community with low vaccination rates.’
While the two international cases of polio paralysis are concerning, experts are resolute that there is currently no cause for panic. Anyone who has had the polio vaccine as a child — whether in sugar-cube or injection form — will be fully protected.
And given the high rates of vaccination, the virus is unlikely to spread.