COVID-19. Monkeypox. And now, the reemergence of polio. It may seem as if the onset of a new disease outbreak lurks at every turn. With scientists finding polio in New York City wastewater, many Americans may be wondering if they should be bracing themselves for the spread of yet another deadly virus.
Howard Forman, MD, professor of radiology and biomedical imaging, as well as public health (health policy), management, and economics, is passionate about teaching others about public health, especially when it comes to vaccines and preventable viral illnesses. His inspiration stems from his sister, a congenital rubella syndrome survivor, whose illness left her permanently deaf. We spoke with Forman about the latest polio outbreak and its implications for public health in the United States.
First of all, what is polio?
Polio is an enterovirus, and it’s transmitted through what we call the fecal-oral route. For most people, it has no symptoms. For about a quarter of people who get the polio virus, they will have mild symptoms that may include fever, gastroenteritis, upset stomach, aches, and so-on—in other words, flu-like symptoms. Most people would not know they have a polio infection because those symptoms are so common to many other infections.
Somewhere around one in 200 to one in 1000 people that get infected with the polio virus will develop poliomyelitis, which is also known as paralytic polio or acute flaccid paralysis but can also include presentations that are less and more severe, including delayed post-polio syndrome with mild disability or acute respiratory failure and death.
In the United States, we haven’t been worried about polio for decades. But now, it’s making headlines after a man in New York was hospitalized with the virus. How did this happen?
I think part of the problem right now is that the vast majority of the population has no memory of polio. If you’re 70 or older, you have real memories of polio—you know what it’s like to see someone who was in the hospital for months or on respiratory machines and iron lungs. But if you’re younger than 70, you don’t have memory of these things. So, it starts getting easier and easier for people to say, “Why do I need the polio vaccine?”.
The patient in New York had come into contact with somebody who had a vaccine-derived polio virus infection, which may have been completely asymptomatic. I’m presuming someone visited him, probably from Europe, because we do think that the polio virus outbreak that we’re seeing in the Rockland, Orange, and greater New York areas is the same genotype as the cases that we’re seeing—or at least the sewage that we’re seeing—around London and Jerusalem. So it’s likely he came in contact with someone from one of those two areas, and he became infected. And because he was unvaccinated and unlucky, he developed poliomyelitis. It is almost impossible to get paralytic polio if you’ve been vaccinated.
What is vaccine-derived poliovirus, and how does it differ from wild poliovirus?
We’re only seeing vaccine-derived poliovirus in the United States. It’s only in Pakistan, Afghanistan, Mozambique and Malawi where we’re still seeing wild type polio in the recent past. There have been two vaccines in wide use to target polio. The inactivated poliovirus [injected] vaccine that’s used in the United States is extremely effective. It requires four shots. But it’s also expensive, and it can only be administered by a health care professional.
The second vaccine, the oral attenuated poliovirus vaccine, has several advantages. The biggest ones are that it is cheap and could be administered by almost anybody. The term attenuated means that the virus is weakened and not virulent. It’s not going to cause disease, but it’s still a living virus. And so when you give me the oral polio virus vaccine, I become infected, and most importantly, my GI tract responds to it by creating specific antibodies. This means I’m relatively protected against both getting and transmitting the virus in the future. It also means that I’m excreting it, causing other individuals to be exposed. And those individuals, even if they’re not being vaccinated actively, can still become immunized. There’s good evidence that shows that the oral vaccine leads people who are not actively vaccinated to gain immunity.
The biggest disadvantage is that about one in a million—maybe a little more than that—who get a series of oral poliovirus vaccinations will get paralytic polio. Once we had a safer vaccine in the United States, we started moving away from it in 1997, and by 2000, we stopped using it altogether and only used the inactivated poliovirus vaccine. The other side effect is that the weakened virus mutates as it is transmitted, and as it mutates, it may regain virulence. Eventually, it’s able to cause paralytic polio again. If everyone is vaccinated, this is a non-issue. The problem occurs when there are under-vaccinated areas. What we’re finding both in the United States right now, as well as parts of Africa, Asia, and Europe, is that there are large pockets of under-vaccinated areas.
Scientists have since found the virus in New York sewers. Should we be bracing ourselves for yet another outbreak?
In all likelihood, I’m not expecting to see a large number of paralytic polio cases. If you have an enclave of 10,000 unvaccinated people, all living in close quarters, and eventually 8,000 get infected, you could have eight cases of paralytic polio within that group. And we would presumably be getting most of them vaccinated during the time of the outbreak.
But the thing about paralytic polio as opposed to COVID is that every single case is avoidable. It’s not like with COVID, where even if you’re vaccinated, we still expect some people to be hospitalized or die. This is a situation where if you’re vaccinated against polio, you’re not going to get poliomyelitis.
How prepared are health care providers to take on incoming cases?
Because we haven’t seen paralytic polio in such a long time, doctors are not necessarily on the lookout for it. We’re trying to educate the physician community and patients to know what to look for. There’s something called pediatric acute flaccid myelitis. This is a very serious condition that occurs in infants. For the last 10 or so years, this has been much more common than polio, and it has some similar overlapping symptoms. It is very possible that there are people out there with poliomyelitis that are being misdiagnosed with acute flaccid myelitis. So we’re trying to warn physicians that if they’re thinking acute flaccid myelitis to also consider polio, and vice versa.
Worldwide efforts have significantly reduced the prevalence of polio, but why has it been so difficult to eradicate altogether?
Because all you need is one pocket of unvaccinated individuals and one traveler from another part of the world with an infection. The traveler can walk into this pocket, and from there it’s just a ricochet effect as the infection starts to spread like wildfire. And we do have under-vaccinated communities in New York.
What does the U.S. need to do to contain these outbreaks?
The biggest thing is communication efforts to everyone, particularly starting in the areas where we know we have outbreaks—New York City, Orange County, Rockland County. We need to get people to recognize that our vaccination efforts are only successful if people continue them. With the exception of smallpox, all of our vaccination efforts are ongoing and it’s to prevent exactly these types of situations. For those of us that grew up at a time when we saw the adverse outcomes of pertussis and mumps and rubella and polio, it’s a lot easier to convince parents to vaccinate. When you stop seeing bad outcomes, you can easily get complacent and think “Why do I want to sully my child’s body with a foreign chemical?”. There’s been an awful lot of misinformation preceding the COVID pandemic, trying to discourage people from vaccination efforts.
What steps can we take to protect ourselves from being infected?
It’s useful to remember that there’s nothing wrong with checking your own vaccination record if you can find it and make sure you’re vaccinated. If you have any questions about it, seek consultation with your physician, who might suggest getting vaccinated if you’re in an area of a high outbreak and you are completely unsure of your vaccination status. Polio is not an unusual vaccination for people. In fact, it’s one of the most common ones in terms of compliance.
Anything else we should know?
I do think there’s a lot of nuance around the vaccine-derived polio virus. The term itself is going to scare people, and the more people learn about the term, it may sound like the vaccine is causing the outbreak. But first of all, we do not use that vaccine in the United States anymore. We haven’t for over 22 years. And secondly, it’s a population health issue, not an individual issue. Nobody who’s getting polio right now in the U.S. is getting it from the vaccine. They’re getting it from infected individuals.