New York’s governor declared a state of emergency after health officials found polio virus in the sewage of five counties – proof that the disease is circulating. The statement also follows a report by the US Centers for Disease Control and Prevention of an unvaccinated person in Rockland County, New York, who was diagnosed with paralytic polio this summer – the first case identified in the United States in nearly a decade .
Understandably, these events have sparked many questions: Why would a case of polio worry officials? What does finding the polio virus in sewage mean? Who should worry about contamination? If someone had the vaccine years ago, are they still protected now?
To learn more about this disease, which most people alive today have never experienced, I spoke with CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington Milken Institute School of Public Health. He is also the author of “Lifelines: A Doctor’s Journey in the Fight for Public Health.”
CNN: So far, there has only been one documented case of paralysis due to the polio virus in New York. Why is a case worrying health officials?
Dr. Leana Wen: An August report from the CDC stated that “even a single case of paralytic poliomyelitis represents a public health emergency in the United States.” This is for two main reasons.
First, polio is a disease with potentially very serious consequences. During its heyday in the 1940s and 1950s, polio left tens of thousands of children paralyzed each year. Thousands died from the virus.
This changed with the introduction of vaccines that are highly effective – more than 99% effective in protecting against paralytic polio. Thanks to mass vaccination campaigns, the last incidence of wild-type polio occurred in 1979 – and it was thought to have been eradicated in the United States. The re-emergence of such a disease, which can have such serious consequences, is a significant threat.
Second, the one case of paralytic polio may be the tip of a large iceberg. Most cases of polio infection are asymptomatic and do not cause paralysis. Symptoms – which can include fatigue, fever and diarrhea – tend to be mild and may resemble those of other viruses. Public health officials are concerned that there are many other people who may be infected with polio and may be unknowingly spreading it.
This is particularly concerning because Rockland County, where the recent paralytic case of the virus was diagnosed, has a polio vaccination rate of just 60%. In some areas of the prefecture, the vaccination rate reaches 37%. These numbers are well below the threshold required for herd immunity, and this means that there are many people in the area who are vulnerable to polio infection and potentially serious consequences.
CNN: What does it mean that the polio virus has been found in the sewage of five counties, including New York?
Wen: Finding polio virus in sewage means one of two things: That there are people actively infected with polio shedding the virus, or that the virus signal may be from people who recently received the oral polio vaccine (OPV). OPV is no longer given in the United States – since 2000, the version used in the US is inactivated polio vaccine (IPV), which is injected – but other countries still use OPV, and it is possible that travelers from those places to shed virus from the vaccine.
In rare cases, weakened virus from people who have just received OPV could cause paralytic polio in unvaccinated people – which is a major reason why OPV is no longer used in the US.
An additional point of concern is that a sewage sample from Nassau County on Long Island has been genetically linked to the case of paralytic polio identified in Rockland County. (The two counties are not contiguous, rather they are about 40 miles apart.) This is further evidence of the community’s largely undetected spread.
CNN: How do people get polio?
Wen: Polio is an infectious disease that can be transmitted in several ways. A main route is fecal-oral, which means that someone can get polio if they come into contact with faeces from an infected person. This can happen, especially in children, by putting objects such as toys contaminated with feces in the mouth.
The polio virus could also be spread through the respiratory tract – for example, if someone who is infected coughs or sneezes and those droplets land around your mouth. It is worth noting that people who are vaccinated could also contract polio and pass it on to others, although they themselves are highly protected from serious disease.
CNN: Should New Yorkers be worried about polio?
Wen: Again, people who have been vaccinated against polio are extremely well protected against paralytic polio and should not be concerned at this point. It should be noted, however, that while IPV is very good at preventing the most severe possible effects of the disease, people who received the vaccine could still be carriers of polio and spread it to others. Those at risk for serious outcomes are the unvaccinated and the undervaccinated, including young children under 6 who have not yet completed their polio vaccine series.
CNN: How many polio shots should someone get?
Wen: The CDC recommends that children receive four doses of IPV. The first is given at the age of 2 months, the second at the age of 4 months, the third between 6 and 18 months and the fourth between 4 and 6 years.
Adults who have never been vaccinated against polio should receive three doses of IPV. The first should be administered as soon as possible, the second one to two months later, and the third six to 12 months after the second.
CNN: If someone got the vaccine years ago, is it still protected? Who should get a polio booster now?
Wen: Protection against serious disease remains strong for many years after vaccination. it is thought to last possibly for a lifetime. There is no need for most vaccinated people to receive more doses.
However, if someone has not completed their initial series of vaccines, they should receive their remaining doses. Some fully vaccinated people may also receive an additional lifetime IPV booster under certain circumstances—for example, if they have direct contact with someone suspected of having polio or if they are health care workers at higher risk of exposure to people with the disease.
CNN: What if you’re not sure if you’ve been vaccinated? Let’s say you don’t remember getting the vaccine, and it’s been years. Is there a blood test you can do to verify either way?
Wen: You could check with your primary care doctor’s office or state health department to see if they have records of your immunizations. If they don’t, and there’s no other way to verify — for example, by asking parents or other relatives or caregivers — you should talk to your health care provider about getting the full polio vaccine series now. There is no blood test that can reliably detect whether you are fully vaccinated against polio.
CNN: What if you or your family members have not yet been vaccinated against the polio virus?
Wen: People who have not yet received doses or are not fully vaccinated should make sure to get the full polio vaccine series right away. This is especially important if they live in or around Rockland County in New York – but really everyone should be up to date with their routine vaccinations.
It was a tragedy decades ago that so many children were permanently paralyzed and even died from polio. This should not happen again, as we have such effective vaccines that can prevent serious consequences of the disease.
