Measles may soon be eliminated from hemisphere

Monday, October 16th 2000, 12:00 am
By: News On 6

By Laura Beil / The Dallas Morning News

An invisible battle will soon end. In the Western Hemisphere, an enemy that has claimed millions of lives is on the brink of surrender.

Health authorities declared all-out war on measles in 1994, just a few years after the virus finished a devastating spree through the United States. During epidemics of 1989 and 1990, the measles virus infected more than 11,000 people and claimed 123 lives.

In the years since, measles has retreated into insolated pockets of Latin America. By the end of December, public health experts hope to declare the virus gone from this hemisphere.

"We are quite confident that measles is on the way out," said Dr. Ciro de Quadros of the Pan American Health Organization, which leads the measles elimination effort. From the Americas, many health experts would like to begin a crusade to banish measles from the world. European countries hope to eliminate measles by 2007; the Middle East and Northwest Africa hope to do so by 2010.

The story might sound familiar. The Pan American Health Organization, known as PAHO, was the first health authority to defeat polio, chasing the disease out of the Western Hemisphere in 1991. Now, world health authorities are on the verge of eradicating polio worldwide.

But measles is a very different foe. At first, many health experts wondered whether PAHO had set an unrealistic, although admirable, goal.

"There was a great deal of skepticism," said Dr. Walter Orenstein, who heads the immunization division of the U.S. Centers for Disease Control and Prevention. Now, he said, the numbers speak for themselves.

In 1990, about 250,000 cases of measles were reported in this hemisphere. Last week, during a conference in Brazil on measles elimination, public health experts reported that only 938 people had contracted measles so far in 2000.

"They're leading the way for the world," Dr. Orenstein said of PAHO.

Measles, spread through coughs and sneezes, is perhaps the most contagious of all infectious diseases. It is so easy to catch that, during the last U.S. epidemic, children became ill simply because they sat in clinic waiting rooms where the measles virus lingered in the air. If any good came of the outbreaks a decade ago, they reminded parents that measles should not be viewed as a harmless childhood rite of passage, said Dr. Gordon Green, who was head of the Dallas County Health Department at the time.

"We didn't fully appreciate as a society that measles was a severe disease that could have tremendous impact," Dr. Green said. Then children began to get sick. The epidemics here and elsewhere occurred because lapses in vaccinations left thousands of children vulnerable. All it took to start an epidemic was a sick person or two bringing the disease to town.

The same scenario could occur again if cracks develop in vaccination coverage. To guard against that possibility, the United States spends about $45 million each year to immunize against measles. The vaccinations are necessary, because as long as measles exists in the world, anyone can carry it to this country. The United States now records less than 100 cases of measles a year, most of them sick children arriving from foreign lands. Any one of those children could touch off an epidemic if their peers were not immune.

Some countries in Central and South America have learned this basic lesson the hard way, Dr. de Quadros said. In 1996, all areas of Brazil except Sao Paulo had made stringent efforts to vaccinate children, he said. In 1997, Sao Paulo was the epicenter of a large outbreak of measles that affected almost 50,000 people. Measles then spread to many countries in South America, but only Argentina – which had also not followed vaccination guidelines – had an outbreak in 1998. From Argentina, measles found three other countries without good vaccination coverage: Bolivia, the Dominican Republic and Haiti, Dr. de Quadros said.

Immunization efforts are now concentrated in those three countries. After those children are immunized, measles will have nowhere in the hemisphere to spread.

But despite PAHO's dramatic progress, eradicating measles won't be easy, Dr. Orenstein said.

Probably the greatest obstacle, he said, is whether politicians have the will to eradicate the disease. Like the polio campaign, the effort would rely largely on the world's wealthier nations. Yet many of those countries do not see measles as a priority, he said, because it is no longer a big killer of their own children. Before the vaccine was developed in the 1960s, about 8 million children worldwide died from measles each year. Today, the 1 million deaths a year are concentrated in sub-Saharan Africa and South Asia.

Complacency about measles is reflected in some wealthy countries' vaccination rates, Dr. Orenstein and his colleagues report in the October issue of the American Journal of Public Health. While about 96 percent of the population in Vietnam is protected against measles, in Japan – a much richer nation not immediately threatened by measles – the coverage is only 68 percent.

"The developed countries of the world need to be convinced to take measles seriously," Dr. Orenstein said.

But many of the obstacles to measles eradication are not under anyone's control. As the number of measles cases falls among children, many adults remain vulnerable. This is in part because unvaccinated adults usually are not targeted in vaccine campaigns, and many adults have never been exposed to measles. In the 1997 Sao Paulo epidemic, many victims were older children or young adults.

In parts of Africa, the AIDS epidemic might also complicate the effort to protect against measles. The measles vaccine works, although it can be less effective when children are infected with the human immunodeficiency virus, which causes AIDS.

Measles vaccine is a live, but extremely weakened, virus. Among children with healthy immune systems, the virus in the vaccine has just enough life to provoke an immune reaction without causing disease. But among children infected with HIV, scientists wonder whether the weakened immune system in some cases wouldn't totally disable virus in the vaccine. In those cases, the children could theoretically become chronic carriers of measles, although this scenario has never been documented.

Public health experts also worry that a vaccine that needs a needle and syringe might not be safely used in the poorest parts of the world. (Polio vaccine is given orally.) In areas where medical supplies are scarce, needles are often reused without sterilization. Unclean needles could spread bloodborne disease. Doctors do not want to see a campaign to eradicate measles become a vehicle for spreading hepatitis B or the AIDS virus.

Yet despite these obstacles, there is reason for optimism, Dr. Orenstein said. Somehow, authorities in Latin America appear to have overcome the challenges.

"It has been done in some of the worst settings you can imagine," Dr. de Quadros said. Much of the success was built on the foundation of polio elimination, he said. The same workers who vaccinated children then are still on the job now.

"You don't create a new infrastructure," Dr. de Quadros said. It's not a special team giving the shots, he said. "It's the health system."

Other health experts agree that a measles eradication campaign will have the most benefit if it concentrates on improving the overall health of children. "What you want to bring is not one vaccine for one disease, but an infrastructure for child health," said Dr. Sam Katz, an immunization expert from Duke University Medical Center.

Dr. Green, now a dean at the University of Texas Southwestern Medical Center at Dallas, hopes he has witnessed his last large measles outbreak. "This is something that we really owe to ourselves and to society – to get rid of this disease," he said. "If we don't, we will probably have a repeat of those outbreaks that occurred, with absolutely needless illness."