An outbreak of polio in recent weeks in the southern African nation of Namibia, which had been free of the disease for a decade, is highly unusual because the disease is striking and killing adults, according to the World Health Organization.
The fast-moving outbreak has killed seven Namibians and paralyzed 33 more, and panicked citizens have deluged hospitals seeking immunization against polio. But there was very little vaccine in the country - only enough for routine vaccination of infants - so supplies quickly ran out and people were turned away.
Once new shipments arrive, it should be relatively easy to bring the outbreak under control, said Dr. David L. Heymann, the WHO director-general's representative for polio eradication. The country's health minister said he did not expect to get a vaccination campaign under way until June 21.
Namibia, a desert country of 2 million people on Africa's southwest coast, is rarely in the news, but it has seen intense coverage in gossip columns recently because Angelina Jolie gave birth there May 27 to her daughter with Brad Pitt.
Polio has been reduced by 99 percent since 1988 and has been hovering on the edge of eradication for years but keeps breaking out in new countries.
Polio normally attacks infants and young children, and causes paralysis in about 1 of 200 of those cases. Children with withered limbs begging on street corners are a common site in parts of Africa and India.
In rare cases, the infection goes up the spine to the brain stem and paralyzes the breathing muscles, killing victims unless they are quickly put on respirators. Mechanical respirators, which blow air into the lungs, have replaced the classic Western symbol of polio - the iron lung machines of the 1950s, which drew in air by pressing on the patient's rib cage.
In the other 199 cases out 0f 200, the virus causes a mild flulike illness or no symptoms at all, and the infected child gains lifelong immunity against the disease.
Because there can be so many of these hidden cases, the appearance of even a few cases of paralysis constitutes a serious outbreak. Afghanistan, for example, has had fewer than 12 cases of paralysis a year since 2001 but has not been able to wipe out the disease.
In adults, the disease is far more serious than in children and is much more likely to paralyze or kill.
Because Namibia is sparsely populated, with a desert climate and cities with paved boulevards, it lacks the overflowing open sewers where the virus thrives during the rainy season in countries like Nigeria and India.
The virus is shed in feces and can be picked up by, for example, touching a soccer ball that has rolled into a gutter and then putting fingers in the mouth. During the outbreak in the 1950s in the United States, public pools were shut down and children were told to watch out for drinking fountains, door handles and anything else that many people touched.
Namibia was a German colony before World War I, though Britain captured it during the war and it became a protectorate of South Africa afterward; it gained independence in 1990. Before independence, which ended a long civil war between Cuban-aided black nationalists and the U.S.-aided white South African government, polio vaccination was not routine in the country. Since 1990, the vaccine has been given only to children under 5, as is normal in the rest of the world, and the country last saw a case of polio in 1996.
As a result, Heymann said, almost no one over 15 in Namibia has any protection from polio: They have not been vaccinated and have no natural immunity from exposure to polio passing through the population.
The first detected case in the current outbreak, he said, was a 39-year-old farmer who went to Windhoek, a city of 125,000, in early May for a gall-bladder operation. He fell ill two weeks after returning to Aranos, his hometown, and is on a respirator.
The known cases in the outbreak, all discovered since then, are largely confined to people over the age of 20 in Windhoek and Aranos.