The historic effort to eradicate polio was jolted last week when the disease reappeared in Indonesia for the first time in a decade, but leaders of the global campaign said they are still confident they will succeed -- and might even make the long-shot target of halting transmission of the virus by year's end.
Since 2003, polio has reappeared in 16 countries that had been free of the paralytic disease for at least a few years, all of it traceable to a strain of the virus that began spreading in northern Nigeria when public fears about the vaccine temporarily stopped immunizations.
A health official gives a boy an oral polio vaccine in Indonesia, which is experiencing its first outbreak in 10 years.
(Imam Sewoko -- AP)
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Despite the latest bad news, health officials said last week that Indonesia, which reported five cases on the island of Java, is moving quickly to suppress transmission of the virus. Polio continues to decline rapidly in the half-dozen countries where person-to-person transmission has never been stopped, and immunization efforts will be bolstered by a new formulation of the vaccine that became available this year.
"I can't tell you that we can't make the target," said David L. Heymann, a physician and epidemiologist with the World Health Organization. "We won't be able to say until August, when the high-transmission season resumes. Then we'll know how many countries still have polio."
Indonesia has "done just about everything right in how they are responding to this outbreak," said Christopher Maher, who heads the WHO office coordinating national polio-eradication efforts.
Late this month, Indonesia plans to begin house-to-house vaccination in three provinces, with a goal of giving two drops of oral polio vaccine to 5 million children younger than 5. The campaign is to be repeated six weeks later. In the meantime, public health officers in West Java are redoubling efforts to look for more cases, he said.
The Polio Eradication Initiative has run into repeated obstacles since it was started in 1988 by the service club Rotary International. It originally hoped to stop polio transmission by 2000. That target moved to the end of 2005, but that date, too, increasingly looks out of reach. The program is now run jointly by Rotary, WHO, the U.N. Children's Fund, and the Centers for Disease Control and Prevention.
The biggest setback by far was the cessation of polio vaccination in several states of northern Nigeria in mid-2003. The country, Africa's most populous, was one of six where the virus was endemic -- freely circulating in human-to-human transmission. The others were Niger, Egypt, India, Pakistan and Afghanistan.
Immunization was stopped in Kano and other Muslim-dominated northern states of Nigeria amid rumors that the eradication campaign was an anti-Muslim plot and that the vaccine would make people sterile or cause AIDS. Among the measures taken to restore confidence was an agreement to use vaccine made in predominantly Muslim Indonesia.
During the 16-month suspension, however, polio flared up and was carried unwittingly by Nigerians to neighboring countries. It ultimately hopscotched across Africa, into the Middle East and most recently into Asia. The latest countries to be hit include Saudi Arabia, which had two cases in late 2004; Yemen, which has had 22 this year; and Indonesia. In six of the reinfected countries -- Ivory Coast, Burkina Faso, the Central African Republic, Chad, Mali and Sudan -- the virus is circulating again, with multiple outbreaks.
For every case that causes muscle weakness or paralysis, experts say, there are 100 to 200 infections that produce only fever and mild illness, or no symptoms. Consequently, when epidemiologists find a few cases, they assume that hundreds of people are carrying the virus and can pass it to others who are not immune through vaccination or prior infection.
Immunization resumed in northern Nigeria last fall and is achieving greater population coverage than before, said R. Bruce Aylward of WHO, who heads the eradication initiative. The effort now has the support of many religious and traditional leaders.
"Now the low-performing areas are getting around 75 percent coverage, and the high-performing areas about 90," Aylward said. "If they can sustain that for four or five rounds [of immunization campaign], they have a real shot at stopping transmission fast."
In 1994, Nigeria recorded 792 cases of polio. This year it has had 54, about half the number at the same time a year ago.
Nigerian President Olusegun Obasanjo, meeting with Washington Post reporters and editors last Thursday, did not respond directly when asked about his country's commitment to polio eradication. But he said the recent experience showed that when issues of health and religion are mixed, "you are dealing with fire."
How polio reached Indonesia is unclear. While the virus in all 16 reinfected countries has been traced to Nigeria, genetic analysis suggests the microbes in Yemen and Indonesia did not get there directly. Instead, they are descendants of the strain that was carried out of northern Nigeria more than a year ago and reappeared across Africa.
"This didn't walk out of Kano last week," Aylward said.
Although initial reports suggested the virus was brought to Indonesia by someone returning from the hajj, the Muslim pilgrimage to Mecca, investigators have not found a direct link to a pilgrim, Maher said. The first case was in an unimmunized 18-month-old.
Among the new tools of the eradication endgame is a slightly different formulation of vaccine that the campaigners hope will boost immunity.
The oral vaccine contains live, weakened versions of all three distinct types of polio virus. Each type has a slightly different ability to bind to receptors on the surface of immune-system cells -- the first step in the cascade of events that results in protection. Type 2 virus binds the most strongly and tends to "outcompete" the other two. Type 2 disappeared in 2000, probably because people had more protection against it.
The dominant remaining strain in the world is Type 1, which is responsible for all the cases traceable to Nigeria. Last year, WHO asked the French pharmaceutical firm Sanofi Pasteur to make a vaccine containing only Type 1. The new vaccine, licensed in March, will help achieve more rapid immunity against Type 1 virus during the mop-up campaigns that follow outbreaks. (Sanofi Pasteur has donated about 120 million doses of vaccine for use in Africa.)
The experts said the ultimate timing of eradication hinges on more than progress in Nigeria. It also depends on whether vaccination campaigns in Ethiopia have prevented further spread of the virus in the Horn of Africa, particularly into the "failed state" of Somalia. It also depends on how quickly the disease can be eliminated from India and Pakistan, which once had the highest rates of transmission.
No cases have been found in Afghanistan this year -- "a major achievement," said Peter Salama, UNICEF's chief of immunization.
William T. Sergeant, 85, a Rotarian from Tennessee who heads the club's polio efforts, called the Indonesia outbreak "not a terrible challenge." He added: "But it is disappointing, I certainly have to say that." Since 1988, Rotary International has spent about $575 million on efforts to eliminate the disease.
The global campaign needs about $50 million more this year than it has available, Heymann said last week. By the end of the year, the 17-year project will have cost about $4 billion.
