Virus World

This report describes a case of polio in an unvaccinated adult resident of New York and highlights why it’s important to stay up to date on recommended poliovirus vaccination. 

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.

Malawi has declared a polio outbreak after a case was detected in a young child in the capital Lilongwe, the first case of wild poliovirus in Africa in more than five years, the World Health Organization (WHO) said. Africa was declared free of indigenous wild polio in August 2020 after going 4 years without a recorded case. Because testing showed that the new case detected in Malawi is linked to a strain from Pakistan, it does not affect Africa’s polio-free status, WHO noted.  “As long as wild polio exists anywhere in the world, all countries remain at risk of importation of the virus,” Matshidiso Moeti, MD, MPH, WHO’s regional director for Africa, said in a statement. The incidence of wild polio has declined nearly 100% since 1988. It continues to be endemic in only two countries, Afghanistan and Pakistan, although only six total cases have been detected in those two countries since the beginning of 2021, according to the Global Polio Eradication Initiative (GPEI).  The GPEI reported that the child in Malawi is a 3-year-old girl who experienced an onset of paralysis on Nov. 19 last year. It said the virus was genetically linked to a strain detected in Pakistan’s Sindh province in October 2019.

“Detection of [wild poliovirus] outside the world’s two remaining endemic countries, Pakistan and Afghanistan, is a serious concern and underscores the importance of prioritizing polio immunization activities,” the GPEI said in a statement. “Until polio is fully eradicated, all countries remain at risk of importation and must maintain high vaccination coverage to protect all children from polio.” According to WHO, health authorities in Malawi have responded to the case with increased surveillance and supplemental immunizations, supported by WHO. Neighboring countries have also ramped up surveillance. A GREI rapid response team based in WHO’s Africa office is deploying to Malawi to support efforts. “Any case of wild polio virus is a significant event, and we will mobilize all resources to support the country’s response,” Modjirom Ndoutabe, MD, polio coordinator at WHO’s Regional Office for Africa, said in a statement.

Using two types of polio vaccines seems to provide stronger protection against the disease and may boost efforts to eradicate polio, a new study shows. The research involving nearly 1,000 children in India found that giving the Salk inactivated poliovirus vaccine (IPV) to those who had already been given the Sabin live-attenuated oral poliovirus vaccine (OPV) appeared to improve their immunity to the virus that causes polio. The findings, reported in the Aug. 22 issue of the journal Science, could prove crucial in eliminating the world's remaining pockets of polio in places such as Iraq and Syria.

"This study revolutionized our understanding of IPV and how to use it in the global eradication effort to ensure children receive the best and quickest protection possible from this disease," study senior author Dr. Bruce Aylward, assistant director-general for Polio, Emergencies and Country Collaboration at the World Health Organization, said in a journal news release. "IPV should be used to accelerate the eradication of the virus in populations that have limited access to vaccination," study author Dr. Hamid Jafari, WHO's director for polio operations and research, said in the news release. "The study has also provided the evidence for use of IPV among travelers to limit further international spread of the virus."

Since polio vaccine was developed in the 1950s, efforts to eradicate polio have relied mainly on OPV rather than IPV. However, these findings show that giving both vaccines to patients may be the best approach. "The global eradication effort is at a critical crossroad," Jafari said. "Endemic polio is increasingly geographically restricted to populations in insecure and inaccessible areas. Yet the virus in these areas persists with incredible tenacity and threatens the increasingly vulnerable populations in polio-free countries with weak or conflict-affected health systems."

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.

Health officials say parents should ensure their children have been vaccinated against the disease.  The virus that causes polio has been detected in a concerning number of sewage samples in London, health officials have said. The disease was common in the UK in the 1950s but was eliminated by 2003. The UK Health Security Agency (UKHSA) says it was probably imported to London by someone who was recently vaccinated overseas with a live form of the virus. It says the risk is low, but parents should ensure their children have been fully immunised against the disease. "Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk," said Dr Vanessa Saliba, consultant epidemiologist at UKHSA. An inactivated polio vaccine is used in the UK as part of the routine childhood programme. It is given to children three times before the age of one, and then again at three and 14 years of age.  Take-up of the first three doses is about 86% in London, well below target levels, with the rest of the UK over 92%. Health authorities have now declared a national incident and informed the World Health Organization (WHO) of the situation.

Four African countries have reported new cases of polio linked to the oral vaccine, as global health numbers show there are now more children being paralyzed by viruses originating in vaccines than in the wild. In a report late last week, the World Health Organization and partners noted nine new polio cases caused by the vaccine in Nigeria, Congo, Central African Republic and Angola. Seven countries elsewhere in Africa have similar outbreaks and cases have been reported in Asia, including the two countries where polio remains endemic, Afghanistan and Pakistan.

In rare cases, the live virus in oral polio vaccine can mutate into a form capable of sparking new outbreaks. All the current vaccine-derived polio cases have been sparked by a Type 2 virus contained in the vaccine. Type 2 wild virus was eliminated years ago. Polio is a highly infectious disease that spreads in contaminated water or food and usually strikes children under 5. About one in 200 infections results in paralysis. Among those, a small percentage die when their breathing muscles are crippled. Donors last week pledged $2.6 billion to combat polio as part of an eradication initiative that began in 1988 and hoped to wipe out polio by 2000. Since then, numerous such deadlines have been missed.

To eradicate polio, more than 95% of a population needs to be immunized. WHO and partners have long relied on oral polio vaccines because they are cheap and can be easily administered, requiring only two drops per dose. Western countries use a more expensive injectable polio vaccine that contains an inactivated virus incapable of causing polio. The Independent Monitoring Board, a group set up by WHO to assess polio eradication, warned in a report this month that vaccine-derived polio virus is “spreading uncontrolled in West Africa, bursting geographical boundaries and raising fundamental questions and challenges for the whole eradication process.” The group said officials were already “failing badly” to meet a recently approved polio goal of stopping all vaccine-derived outbreaks within 120 days of detection. It described the initial attitude of WHO and its partners to stopping such vaccine-linked polio cases as “relaxed” and said “new thinking” on how to tackle the problem was needed.

W.H.O. Report (November 20, 2019)  available at :

http://polioeradication.org/polio-today/polio-now/this-week/