Nigeria polio strain in Indonesia

Molecular epidemiology reveals path virus took from Africa to Asia, CDC expert says

By | May 10, 2005

An outbreak of poliomyelitis in the Indonesian region of West Java has so far seen four people in and around the village of Giri Jaya confirmed with the disease, the Global Polio Eradication Initiative said on Tuesday (May 10).

The outbreak of the disease marks reappearance of wildtype polio in Indonesia for the first time since 1995. Molecular epidemiologists working for the US Centers for Disease Control and Prevention (CDC) have in the past few days clarified the likely route the virus took from Nigeria to Indonesia.

"It's very likely a direct exportation. We ran it through our database and it matched up closely with an isolate from Saudi Arabia," Olen Kew, chief of the molecular virology lab at the CDC in Atlanta, Georgia, told The Scientist.

Some press reports have suggested that Saudi Arabia or the Sudan might be the immediate source, Kew said, but "the genetic data suggest that most likely pathway was Nigeria to Chad to Sudan to Saudi Arabia to Indonesia."

Kew's recent analysis of the "molecular clock" from Indonesian isolates has not yet revealed when polio likely entered Indonesia, but he hopes further study of subsequent isolates might. Interviews with the victims' families haven't revealed an obvious link to Saudi Arabia.

"There is a 2- to 4-month gap here, and we are at the limit of what our genetic data can distinguish. We'll widen the genetic sequencing window which is what is used to establish the link," said Kew. A recent CDC study demonstrated that at least 14 previously polio-free countries had importations of strains from the Nigeria-Niger endemic strains of 2003 and 2004.

"Nigeria is a highly endemic country; it's the heart of the poliovirus circulation in Africa," said Christopher Maher, chief epidemiologist for the World Health Organization's (WHO's) polio eradication group. Unfounded rumors the inoculation was made unsafe as part of a Western plot to make Muslim children infertile caused several northern Nigerian provinces to stop vaccination campaigns in 2003. The suspension, lasting 12 months in some areas, seeded polio outbreaks across central Africa countries.

The CDC report also revealed that low-level transmission of both wild type 1 poliovirus and type 3 poliovirus had been going unnoticed in Sudan and Chad for several years. Later, it became clear that conflict in Darfur contributed to surveillance gaps.

"A large outbreak occurred in Sudan that moved rapidly from West to East to Port Sudan on the Red Sea coast and essentially jumped across the Red Sea into Saudi Arabia," said Kew.

There's no evidence that polio circulates in Saudi Arabia, but there's no doubt polio has reestablished itself on the Arabian Peninsula. On April 29, Yemen reported its 22nd polio case.

Until the discovery of a handful of cases a few weeks ago, Yemen had been considered polio-free since surveillance for the disease began in 1996. "The poliovirus in Yemen is also from Sudan but is a separate chain of transmission [to that which reached Indonesia]," said Kew.

Armed conflict and interrupted immunizations go hand in hand in Africa. The CDC report also described missed days of mass vaccination in Côte d'Ivoire due to violence.

The molecular epidemiology reveals weaknesses in surveillance in Africa, Kew told The Scientist. "Surveillance in Sudan and Chad and other parts of Central Africa haven't been as good as we had hoped," he said.

Despite the much talked about renewed spread of polio in Africa, the Global Polio Eradication Initiative, started in 1988, has made progress. Countries like Pakistan, Afghanistan, and India have all reported decreases in cases.

This year, 21 African nations held a couple of synchronized "National Immunization Days" between February and April. Three more rounds are planned as a response to the disease's reemergence. "The quality of those rounds was much better than in 2004," said Maher.

Indonesian authorities plan to begin a mop-up campaign in West Java, Banten, and Jakarta provinces between May 31 and June 2, and again between late June and early July. The aim is to vaccinate all of the children under the age of 5 in those provinces. Maher, who together with Indonesia health authorities conducted the follow-up on the West Java cases, has confidence in the response. "Indonesia makes [oral polio] vaccine, it's registered and ready," he said.

The polio outbreak in Yemen is more worrying to health experts because of the speed with which it spread across the country. "The risk to neighboring countries is pretty high, as is the likelihood that we'll end up with a lot more cases in Yemen," said Maher.

WHO said on Tuesday that six million doses of monovalent oral polio vaccine type 1 have been shipped to Yemen to help to stop the ongoing polio outbreak. The vaccine is expected to arrive in Yemen early next week for use in the nationwide immunization campaign to be conducted at the end of the month.

A WHO emergency slush fund reserved for tackling polio outbreaks is all but depleted, according to Maher. Money had been directed to Ethiopia to help run a national immunization campaign, but WHO is appealing to member countries to come up with funding for Yemen.

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