Impact of the New York polio outbreak on global eradication efforts

For the first time in almost 10 years, For polio Confirmed in the USA. Health officials in New York’s Rockland County last month said: unvaccinated 20 year olddecades after polio was eradicated from the United States 1979.

Countries and public health systems are already under pressure COVID-19 When monkeypox, this news comes as an unpleasant surprise and immediately raises the question.Who else is at risk? Vaccine-derived strainand what are the implications for global efforts to eradicate polio?

What is polio?

Polio, short for polio, is caused by the poliovirus, an enterovirus that infects the nervous system. Symptoms are flu-like (sore throat, fever, fatigue), causing more serious infections of the spinal cord meningitis and even paralysisBut unlike the flu, the poliovirus grows primarily in the intestine. If you don’t wash your hands after using the toilet, it will spread.Polio is highly contagiousat least in unvaccinated people, especially in areas with infectious diseases poor hygiene and water safety.

from US outbreak first documented in 1894 Polio was one of the deadliest diseases until a vaccine was developed in the 1950s. feared childhood illnessThousands of children left behind paralyzed Occurs every summer.was the most vulnerable child Under 5 years old.

But those victims were the exception. His three-quarters of poliovirus-infected patients show no symptoms at all.The disease will not progress beyond that for most of the remaining quarter flu-like symptomsHowever, in approximately 1 in 25 patients, the virus spreads to the nervous system and causes meningitis. About 1 in 8 people with meningitis, or about 0.5% of all polio cases, suffer permanent nerve damage and become paralyzed. No cure was known. artificial lung — since being replaced by more advanced ventilators — and physical therapy.

The polio threat was made permanent when two vaccines were briefly discovered: the inactivated vaccine injected by Dr. Jonas Salk in 1955 and the live attenuated vaccine taken orally by Dr. Albert Sabin in 1961. has changed. effective, Gives 99% immunity against infectionSabin’s oral vaccine was eventually widely adopted in the United States, and in the 1960s and 70s polio cases declined dramatically and the wild virus was completely eradicated in the country.

America was ahead of its time. In 1988, a few years after smallpox was declared eradicated in 1980, a global vaccination campaign began in earnest. switched In 2000, a slightly safer inactivated injectable vaccine was introduced. Standard childhood vaccination schedulearound the world, thanks Ongoing Public Health Effortswith hundreds of millions of children receiving oral vaccines each year, the original wild virus is driven out of all others. a handful of countries.

Where did this case come from?

Since the local polio epidemic was eliminated in the United States around 1980, all infections have come from other countries still infected with the disease. gene sequencing indicate that the most recent case was a vaccine-derived strain of poliovirus. This is because the circulating virus has mutated from a live oral attenuated vaccine, which is not the vaccine currently in use, rather than from one of the few remaining areas where endemic wild poliovirus remains. Means it is from one of the more countries where it originated. in the United States.

Polio vaccine is two kinds: inactivated or live attenuated. live attenuated vaccineas combined Measles, mumps, rubella Vaccines recommended for all children in the United States contain modified, weakened strains of pathogens that do not cause disease in humans, but provoke an immune response that protects against the original strain. The oral vaccine used in countries where HIV is present is a live attenuated vaccine. Inactivated vaccines, such as the polio vaccine currently in use in the United States, contain only dead viral material, Longer series of booster shots Sufficiently stimulates the immune system to provide long-term complete immunity.

Live attenuated poliovirus vaccines rarely cause polio itself, but Less than 1/1,000,000 The fact that they contain live virus, unlike inactivated vaccines, entails risks if the child is severely immunocompromised.When inoculated with live attenuated polio vaccine in the community Due to the high proportion of unvaccinated people, modified viruses can infect others. Enough Diffusion generation, can very rarely mutate and revert to new pathogenic strains. Ensuring that enough people are vaccinated to protect against both wild viruses and potential new vaccine-derived strains is essential to public health efforts.

Ironically, the fact that most polio cases are asymptomatic or mild, take up Up to 30 days before symptoms appear — polio is particularly difficult for contact tracing and public health containment efforts. The only way to keep the virus under control is to achieve the herd immunity needed for polio. About 80% of the population vaccinated.

WHO IS AT RISK?

For most people in the United States, newly discovered polio cases do not pose any increased risk. no longer contagious.

Poliovirus is Detected from fecal samples,and again Wastewater monitoring, looking for evidence of viral genetic material in sewage. August 1, New York State Department of Health report The Rockland polio case was genetically linked to virus samples collected in the United States. sewage In Jerusalem and London, the department stressed that results do not automatically mean that the patient has traveled anywhere. Rockland Public Health was able to use previously collected sewage samples for Covid-19 surveillance. The poliovirus was found in the samples there. from June Genetically related to the current case.

Given how common asymptomatic cases are and the long incubation period, it is possible that there are other unrecognized cases in the Rockland region. They may still be contagious, but it’s unlikely to spread far. Over 90% of U.S. Children Fully vaccinated against polio on schedule and well above herd immunity threshold. unchanged for decades. Infants over 4 months I usually get 2 doses, but this is already Provides 90% immunity.

However, Rockland County has lower vaccination coverage than other regions.was the site of 2018-2019 measles epidemicand currently only 60% of 2 year olds People are fully immunized against polio, compared to the national average of 90%.of New York State Department of Health For those who are not currently vaccinated, who have not completed the polio vaccination series, and who are pregnant, get vaccinatedIn the month since polio cases were discovered, the Rockland Clinic About 400 vaccinationsPeople in the Rockland area who were vaccinated as children but are worried they might have become infected should schedule booster shots.

What does this mean for global eradication efforts?

The United States is protected from polio, but the same cannot be said for developing countries at risk where the virus is still active.

After working on an oral vaccine, Sabin launched a global eradication campaign in the 1960s and 1972. donated all of his vaccine strains to the World Health Organization in hopes of reducing manufacturing costs.Despite recent efforts to introduce a slightly safer inactivation vaccines around the worldmost low- and middle-income countries remain oral vaccine.

of global eradication program was huge success overall, total Decline in global polio cases It has increased by more than 99.99 percent since the program began in 1988. closer Eradication becomes difficult reach the finish lineWhen hundreds of millions of oral vaccines are administered each year, even the very low risk of creating new strains of vaccine-derived strains is added. African countries favorite Nigeria and Yemen that is vaccination-derivation. Interruption of vaccination military conflict and the COVID-19 pandemic likely increased the risk of Vaccine-derived variants It spreads defenselessly.

Despite the risks inherent in live-attenuated vaccines, oral vaccines have significant advantages for public health campaigns, especially in developing countries.Each dose is small 12 centscompared to about $2 once Inactivated vaccines are dropped under the tongue and do not need to be administered by a needle or trained professional. .

And early on, it was thought that the infectivity of oral vaccine strains was actually positive. Children who are unreached by health workers may catch weakened strains from others and gain immunity. of people, the spread will subside long before the virus mutates back to human virulence.

Phase out of oral vaccinesEliminate the source of new polio variants too low To cover the hundreds of millions of children who are still at risk.

By contracting monkeypox recently declared a public health emergency Growing international attention by WHO, and ever-present Threat of future pandemics In the near future, the global effort against polio will be more important than ever to ensure that polio never again becomes such a global threat. Under maintenance When ideally increase U.S. vaccination coverage will help protect the nation for the foreseeable future and help global efforts to eradicate polio by removing its foothold.