On Thursday, New York state health officials stepped up efforts for people who have not been vaccinated against polio to get vaccinated “immediately”, saying the only confirmed case of the disease found in the state could be “the tip of the iceberg” of a much larger threat.
The urgent appeal came as officials said polio had been detected in sewage samples taken from multiple locations and at different times in two counties north of New York, potentially signaling community spread of the disease .
“Based on past polio outbreaks, New Yorkers should know that for every case of paralytic polio observed, there may be hundreds more infected,” Dr. Mary T. Bassett, state health commissioner, said in a statement.
“Coupled with the latest sewage findings,” Dr. Bassett added, “the department is treating the single polio case as the tip of the iceberg of a much larger potential spread.
Poliomyelitis is caused by the poliovirus and children under 5 are most at risk of contracting it, but anyone who has not been vaccinated is at risk. Poliomyelitis is highly contagious and is usually passed from person to person when a person comes into contact with an infected person’s feces and then touches their mouth.
The fight against poliomyelitis
The highly contagious virus was one of the most feared diseases until the 1950s when the first vaccine was developed.
Many cases are asymptomatic and some can cause flu-like symptoms, but the disease, also known as poliomyelitis, can be debilitating and even fatal. There is no remedy.
Paralysis is a rare outcome, but before vaccines became widely available in the 1950s, polio epidemics caused over 15,000 cases of paralysis per year.
Last month, a case of polio — the first to be reported in the United States in nearly a decade – was identified in an unvaccinated adult male in Rockland County. No cases had appeared in the United States since 1979.
State and county health officials said infection in Rockland County had been transmitted by someone who received the oral polio vaccine, which has not been administered in the United States since 2000.
The virus circulating in New York may have come from outside the United States, where the oral vaccine is still administered, officials said. The oral vaccine contains a weakened virus. It is safe, but if a vaccine-derived virus circulates in a community, it can infect unvaccinated people and spread disease.
In announcing the case, officials stressed that the infected person was no longer contagious and said their efforts would focus on increasing vaccination rates and determining if anyone else might have been affected.
Officials said polio was found in samples of Rockland County sewage collected in June, before the polio case was confirmed. On Thursday, they said evidence of the disease was also found in sewage samples taken in June and July from two “geographically different” parts of Orange County, adjacent to Rockland.
“The results,” the state health department said in a news release, “provide further evidence of local — not international — transmission of a polio virus.”
There is no evidence that the infected man in Rockland County was the source of the polio found in the sewage samples, officials said. The investigation into the origin of the virus continues.
Because large-scale vaccination has proven to be an effective prevention strategy, areas with low vaccination rates may be particularly at risk of outbreaks.
In Rockland and Orange counties, approximately 60% of 2 year olds received all three doses of the polio vaccine, according to state data – a rate considerably lower than the 80% in the rest of the state except New York. (To obtain herd immunity against poliomyelitis, the target vaccination rate is 80%, according to the World Health Organization.)
Most adults in the United States do not need to be vaccinated against polio because they most likely were immunized as children, although some may be eligible for booster shots if they are at increased risk of exposure .