Virus World

Health department says it's working with Jerusalem 'to ensure a coordinated response' after 4 cases of virus recently detected in Safed. The State of New York’s health department called for residents to get vaccinated against polio before traveling to Israel, where several children have recently tested positive for the virus. In a statement Friday, the New York Department of Health noted the four cases diagnosed in the northern city of Safed earlier this month, a year after a small outbreak of the disease in the country. It called on New Yorkers “to get fully immunized” before flying to Israel or other countries with polio. Health officials in New York have been in touch with their Israeli counterparts “to ensure a coordinated response,” the statement said, adding that travelers should adhere to guidelines from the US Center for Disease Control. Besides Israel, the statement noted the CDC has issued precautions against polio before traveling to the United Kingdom, Ukraine, Afghanistan, Pakistan, Indonesia, Nigeria, Côte d’Ivoire and several other central African countries.

Polio is a viral disease that mainly affects children and can cause disability, paralysis and death. Today, polio vaccinations are standard for children and are an effective preventive measure, but vaccine skepticism has enabled the disease to pop up from time to time. The outbreak in Israel last March, which came after the first case of polio in 33 years was discovered in the country, prompted a vaccination drive to combat the disease. The finding landed Israel on the World Health Organization’s Polio Eradication Initiative’s list of countries with outbreaks, after it was declared polio-free in 1988. Following the cases detected earlier this month, the Health Ministry cited evidence of polio spreading in sewage systems and said over 150,000 Israeli children are unvaccinated against the virus.

The following essay is reprinted with permission fromThe Conversation, an online publication covering the latest research. The first case of polio in the U.S. since 2013 was announced by New York state health officials on July 21, 2022. The U.S. resident had not been vaccinated. Polio was a common cause of paralysis in children before safe and effective vaccines were invented in the mid-20th century. Thanks to global vaccination campaigns, polio is now almost eradicated, with only 13 cases of endemic wild poliovirus reported in 2022 to date worldwide.  The New York patient reportedly contracted a form of polio that can be traced back to the live, but weakened, poliovirus used in the oral polio vaccine. This version of the vaccine has not been used in the U.S. since 2000. Health officials said the virus affecting the male patient, who has muscle weakness and paralysis, likely originated somewhere overseas, where oral vaccines are still administered. William Petri is an infectious disease specialist and chair of the World Health Organization’s Polio Research Committee. Here he explains what vaccine-derived poliovirus is and why the inactivated polio vaccine administered in the U.S. today can’t cause it. 

What are the two kinds of polio vaccine?

Vaccines introduce a harmless version of a pathogen to your body. The idea is that they train your immune system to fight off the real germ if you ever encounter it. The oral polio vaccine, originally developed by Albert Sabin, uses a live but weakened poliovirus that one swallows in a sugar cube or droplet. Scientists weaken – or attenuate – the virus so it can no longer cause disease.  The other kind of polio vaccine was originally developed by Jonas Salk. It contains inactivated, dead virus. It is administered by an injection. In the U.S., children receive the inactivated polio vaccine at 2, 4 and 6 months of age. It provides nearly complete protection from paralytic polio.

How can the live vaccine lead to a case of polio?

The weakened form of the live virus in the oral vaccine cannot cause disease. However, because the vaccine is given orally, the weakened virus is excreted in the feces and can spread from someone who is vaccinated to their close contacts. If the weakened virus circulates person to person for long enough, it can mutate and regain its ability to cause paralysis. The mutated virus can then infect people in communities with poor sanitation and low vaccination rates, causing disease and even paralysis.  This is an exceedingly rare occurrence. With more than 10 billion doses of the oral polio vaccine administered since 2000, there have been fewer than 800 cases of vaccine-derived polio reported. Apparently, the current patient in New York was somehow exposed to a mutated poliovirus that had been transmitted after vaccination overseas. Earlier this summer, routine surveillance spotted vaccine-derived poliovirus in London’s sewage system, but no cases have been reported there.

Why use the oral vaccine anywhere if it comes with this risk?

There’s a positive aspect to the fact that the weakened live virus can circulate in the community once oral vaccine recipients shed it in their feces. Traveling a feces-to-oral route, it can help induce immunity even in people who weren’t directly vaccinated. The oral polio vaccine is also cheaper and easier to administer than inactivated polio vaccines. Most importantly, the live-virus vaccine stops transmission of wild poliovirus in a way that the inactivated-virus vaccine does not. The eradication of polio in the Americas, Europe and Africa has been accomplished solely through the use of the live oral vaccine. Once polio has been wiped from a continent, then it is safe to stop using the oral live vaccine and use only the inactivated vaccine, which does prevent disease in recipients and does not pose the rare risk of vaccine-derived paralytic polio.  A new and safer oral polio vaccine that has been engineered not to mutate is now replacing the earlier live-virus vaccine. Thus, even this extremely rare complication of polio vaccination should soon become a thing of the past. 

How close is the world to eradicating polio?

Thanks to tremendous global effort, two of the three viruses that cause polio have been eradicated. The world is now on the verge of eradicating the final one, wild poliovirus 1 (WPV1). Today endemic polio is found only in Pakistan, with 12 cases of paralytic polio so far in 2022, and Afghanistan, with just one case this year. Africa has two cases, imported from overseas, which are being contained by additional vaccination campaigns. Once wild poliovirus has been eradicated from the planet, vaccination efforts may be able to switch to the inactivated polio vaccine, eliminating the risk of any future vaccine-derived cases.

This article was originally published on The Conversation. Read the original article.

New York State reported Thursday that it has detected a case of vaccine-derived polio in a person in Rockland County, north of New York City, the first such recorded case in the United States since 2013.  The unidentified individual developed paralysis, said Beth Cefalu, Rockland County’s director of strategic communications. Polio paralysis is irreversible. The area where the case was detected was the epicenter of a large measles outbreak in 2018-2019 that was fueled by low vaccination rates among communities of Hasidic Jews. The outbreak went on for so long that the country almost lost its measles-free status. The memory of that episode is provoking concern that the area might be ripe for additional vaccine-derived polio cases to occur. “I think it’s concerning because … it can spread,” said Walter Orenstein, a polio expert at Emory University. “If there are unvaccinated communities, it can cause a polio outbreak.” “The inactivated polio vaccine we have is very effective and very safe and could have prevented this,” he said. “We need to restore our confidence in vaccines.” The Centers for Disease Control and Prevention said in a statement that while the risk is low for people who are vaccinated, there is risk for those who have not had the recommended three doses of injectable polio vaccine. “Most of the U.S. population has protection against polio because they were vaccinated during childhood, but in some communities with low vaccine coverage, there are unvaccinated people at risk,” the statement said. “Polio and its neurologic effects cannot be cured, but can be prevented through vaccination.” 

The New York State department of health said in a statement that the person was infected with a type 2 vaccine-derived poliovirus, which would have come from oral polio vaccine used in a number of countries, but not the United States. The U.S. stopped using oral polio vaccine in 2000. Cefalu told STAT the case is still being investigated, but it is believed the individual had not recently traveled outside the country to a place where type 2 vaccine-derived polio viruses are spreading. If that is the case, that would indicate someone else inadvertently imported the virus, suggesting there may be additional undetected transmission. Only a small portion of people infected with polioviruses will go on to be paralyzed.  Kimberly Thompson, a polio expert who is president of the nonprofit organization Kid Risk, said it’s not a surprise to see a vaccine-derived case pop up in this country, noting public health authorities in the United Kingdom recently discovered vaccine-derived polioviruses  in sewage in London, indicating some transmission there.  “With Covid having disrupted immunization (even in the U.S.) and travel now having resumed and much more type 2 poliovirus transmission happening … it’s been only a matter of time before we’d have some detection of polioviruses in sewage, as happened recently in the U.K, or more tragically, a case,” Thompson told STAT in an email. “There’s just a lot more polio going around than there should be.” The oral vaccine contains live but weakened polioviruses, which immunized children excrete in their stools. In places where hygiene is poor, these viruses can spread from child to child, immunizing others as they do. But as they spread, the vaccine viruses can regain the power to paralyze. Such cases are called vaccine-derived polio.  The United States uses injectable polio vaccine that contains killed viruses to teach the immune system to recognize and fight off polio. It cannot cause paralysis.

Mary Bassett, New York State’s health commissioner, said people who are vaccinated against polio do not face a risk from the newly discovered case. But children who are not immunized against the virus should receive the vaccine. “Based on what we know about this case, and polio in general, the Department of Health strongly recommends that unvaccinated individuals get vaccinated or boosted with the FDA-approved IPV polio vaccine as soon as possible,” Bassett said. Rockland County will host vaccine clinics on Friday and Monday, the department’s statement said. The United States used to have upwards of 20,000 paralytic polio cases a year in the early and mid-1950s, Orenstein said, recalling that as a 7-year-old in 1955 he was reluctant to be vaccinated when the Salk polio vaccine — the injected form — was released. “My mother said to me: ‘Better you should cry than I should cry,’’’ he said. With the advent of effective polio vaccines, the disease retreated in much of the developed world. The last recorded case of domestically acquired wild polio was in 1979, though there was an imported case in 1993. But over the years there have been rare imported cases of vaccine-derived polio, from countries where the oral vaccine is still in use. Orenstein said detecting where the virus in the New York case came from is critical. That work can be done by comparing the genetic sequence of the individual’s virus with others in a database the polio eradication program maintains. The world has been trying to eradicate polio for decades, with two of the original three types of polio — types 2 and 3 — having been driven out of existence. But the remaining version, type 1, has defied efforts to end its spread to date. Wild-type polio cases are at low numbers; the viruses are only endemic at this point in Afghanistan and Pakistan, which have recorded a total of 12 cases this year. But recently it was discovered that viruses from Pakistan had made their way to Malawi and Mozambique, a highly unwelcome development. Meanwhile, the numbers of vaccine-derived cases have exploded in Africa and some other parts of the world after the failure of an effort in 2016 to take type 2 viruses out of the oral vaccine. It was felt that given the fact that wild type 2 viruses no longer existed, it was not ethical to use oral vaccine containing type 2 viruses, because of the risk they would regain the power to paralyze.

In a coordinated move called “the switch,” countries around the world were told to stop using trivalent oral vaccine — vaccine that contained all three types of polioviruses — and begin to use a bivalent form that did not include type 2. In the years since, chains of transmission of type 2 vaccine-derived virus have spread to more than 40 countries around the world and the polio eradication program has struggled to contain the spread. So far this year 167 children in 12 countries have been paralyzed by type 2 vaccine viruses, not including the individual in New York. The Global Polio Eradication Program, which leads the effort to rid the world of polio, said in a statement that the discovery highlights the importance of countries continuing to be on the lookout for polio, noting “any form of poliovirus anywhere is a threat to children everywhere.” “It is vital that all countries, in particular those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance in order to rapidly detect any new virus importation and to facilitate a rapid response,” the statement said. “Countries, territories, and areas should also maintain uniformly high routine immunization coverage … to protect children from polio and to minimize the consequences of any new virus being introduced.” The polio eradication program is a partnership involving the World Health Organization, the United Nations Children’s Fund, the service group Rotary International, the Centers for Disease Control and Prevention and the Bill and Melinda Gates Foundation.

New York Gov. Kathy Hochul (D) on Friday declared a state of emergency after poliovirus was detected in the sewage of a fourth county in the state in an effort to boost vaccination rates as some regions lag well behind national vaccination levels.

KEY FACTS

The health department said it is still investigating the virus' origin, after finding eight of the positive wastewater samples are genetically linked. New York state health officials have found indications of additional cases of polio virus in wastewater samples from two different counties, leading them to warn that hundreds of people may be infected with the potentially serious virus.  Just two weeks ago, the New York Health Department reported the nation's first case of polio in almost a decade, in Rockland County, north of New York City. Officials said that case occurred in a previously healthy young adult who was unvaccinated and developed paralysis in their legs. Since then, three positive wastewater samples from Rockland County and four from neighboring Orange County were discovered and genetically linked to the first case, the health department said in a press release on Thursday, suggesting that the polio virus is being spread within local communities. The newest samples were taken from two locations in Orange County in June and July and one location in Rockland County in July. "Based on earlier polio outbreaks, New Yorkers should know that for every one case of paralytic polio observed, there may be hundreds of other people infected," State Health Commissioner Dr. Mary T. Bassett said. "Coupled with the latest wastewater findings, the Department is treating the single case of polio as just the tip of the iceberg of much greater potential spread. As we learn more, what we do know is clear: the danger of polio is present in New York today."  The health department reiterated that it is still investigating the virus' origin, and said that it is not yet clear whether the infected person in Rockland County was linked to the other cases.

Polio is "a serious and life-threatening disease," the state health department said. It is highly contagious and can be spread by people who aren't yet symptomatic. Symptoms usually appear within 30 days of infection, and can be mild or flu-like. Some people who are infected may become paralyzed or die. Before the polio vaccine was introduced in the 1950s, thousands of Americans died in polio outbreaks and tens of thousands, many of them children, were left with paralysis. After a successful vaccination campaign, polio was officially declared eradicated in the U.S. in 1979.   Unvaccinated New Yorkers are encouraged to get immunized right away, the health department said. Unvaccinated people who live, work or spend time in Rockland County, Orange County and the greater New York metropolitan area are at the greatest risk. Most school-aged children have received the polio vaccine, which is a four-dose course, started between 6 weeks and 2 months of age and followed by one shot at 4 months, one at 6 to 12 months, and one between the ages of 4 and 6. According to the health department, about 60% of children in Rockland County have received three polio shots before their second birthday, as have about 59% in Orange County — both below the 79% statewide figure.  According to the CDC's most recent childhood vaccination data, about 93% of 2-year-olds in the U.S. had received at least three doses of polio vaccine. Meanwhile, adults who are not vaccinated would receive a three-dose immunization, and those who are vaccinated but at high risk can receive a lifetime booster shot, according to the health department.  The vaccine is 99% effective in children who receive the full four-dose regime, health officials said. "It is concerning that polio, a disease that has been largely eradicated through vaccination, is now circulating in our community, especially given the low rates of vaccination for this debilitating disease in certain areas of our County," Orange County Health Commissioner Dr. Irina Gelman said. "I urge all unvaccinated Orange County residents to get vaccinated as soon as medically feasible." Rockland County Department of Health Commissioner Dr. Patricia Schnabel Ruppert issued a similar statement, calling on people who are not vaccinated to get the shots "immediately." Polio has rarely appeared in the U.S. since it was declared eradicated over 40 years ago. The last reported case was brought by a traveler in 2013, according to The Associated Press.