As physicians who vaccinate children, we are becoming too complacent about polio. The risk has not disappeared. On the contrary, it’s just a plane ride away.
Dr. Mary Anne Jackson
Of recent concern, an ongoing outbreak of polio in Tajikistan and possibly Uzbekistan represents the first importation of polio in the World Health Organization European Region since it was certified polio free in 2002. I find this alarming, and I believe that the media has not given it enough attention.
As of this spring, the Tajikistan Ministry of Health has reported 432 cases of acute flaccid paralysis, of which 129 were confirmed as polio. Of the confirmed cases, 107 were children aged 5 years or younger. Twelve deaths were reported.
In Uzbekistan, several cases of acute flaccid paralysis have been reported near the border with Tajikistan, according to the Centers for Disease Control and Prevention (CDC). The recent flooding in nearby Pakistan is also cause for concern, because the disease remains endemic there and may be easily spread in the unsanitary conditions that exist now.
Indeed, Pakistan is one of four countries in which wild poliovirus circulation has never been interrupted. The other three are India, Afghanistan, and Nigeria. But since 2005, imported poliovirus has been reported in a long list of countries. In the past year, those have included Angola, Chad, Ethiopia, Indonesia, Nepal, Somalia, and Uganda.
We had been doing well prior to 2005. Between 1988 and 2004, global eradication efforts – in particular, the Global Polio Eradication Initiative – reduced the number of polio cases from 350,000 annually to a low of 1,189 cases. But in 2005, the number of cases rose again to 1,831 from an epidemic that originated in northern Nigeria and spread to 21 previously polio-free countries.
Here in the United States in 2005, the Minnesota Department of Health identified four cases of poliovirus infections in unvaccinated children who were members of an Amish community. The index case, a 7-month-old girl who was confirmed to have severe combined immune deficiency following admission for failure to thrive and pneumonia, was found to have poliovirus in her stool culture, which was confirmed to be vaccine derived. Neither the index patient nor her family had any history of international travel. The CDC determined that the source of the virus was most likely a person who had received the oral poliovirus vaccine (OPV) in another country.
This report was the first identification of a vaccine-derived poliovirus in the United States and the first occurrence of transmission in a community since OPV vaccinations were discontinued in 2000 (MMWR 2005;54:1053-5). None of those children developed paralytic disease, but the CDC issued a warning nonetheless, pointing out that the virus is considered to have potential for wider transmission and for causing paralytic disease.
Since 2005, while cases have been reported elsewhere in the world, we’ve not heard about any in the United States. I fear that with many parents now requesting that some vaccinations be delayed or skipped entirely, it will be tempting for clinicians to select out the polio vaccine simply because they haven’t seen polio and therefore perceive it as less of a threat.
But it isn’t. Families travel to all parts of the world with their children. Teenagers travel on educational and charitable missions. And of course, people from all over the world visit the United States. Polio could easily return here if we become complacent about vaccinating.
We must continue providing the inactivated polio vaccine (IPV) to children at ages 2 months, 4 months, 6-18 months, and 4-6 years. Travelers who have incomplete or unknown immunization status should also receive three doses of IPV (two doses at 4- to 8-week intervals).
We succeeded in eradicating smallpox, and now polio is slated to be next on the list. This is no time to let our guard down.
Dr. Jackson is chief of pediatric infectious diseases at Children’s Mercy Hospital, Kansas City, Mo., and professor of pediatrics at the University of Missouri–Kansas City. Dr. Jackson said she had no relevant financial disclosures to make.