Polio Eradication Effort on Target

Released from Washington, DC

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Harry Hull, MD, WHO expert on global polio eradication, will be available for interviews in Washington, DC on Friday, May 1. Please call (703) 820-2244 to schedule an interview.

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Polio, once one of the world’s most feared diseases, is on track for global eradication by the year 2000 in a campaign that has given 1.5 billion vaccinations to children in the developing world this decade, says a new report by the WHO’s Global Programme for Vaccines and Immunization.

“But the most difficult stage in this struggle still lies ahead, comparable to a mountain climb where the steepest part comes right before reaching the summit,” says Harry Hull, MD, in charge of the World Health Organization (WHO) global polio eradication initiative. “Achieving eradication within our timetable will be especially hard in Africa.”

In 1997 alone, some 450 million children, or two out of every three children under the age of 5 worldwide, were vaccinated in mass campaigns that aim to stop the spread of polio. In 1996, 420 million children under the age of five were vaccinated; in 1995, 300 million children — almost half the world’s population of children less than 5 years of age — were immunized. A single dose of oral polio vaccine (OPV) normally provides just 30-40 percent protection. Therefore, each child should receive multiple OPV doses.

Today, the WHO estimates that between 10-20 million people of all ages are living with polio paralysis, which cannot be reversed.

Following initial successes by the Pan American Health Organization in the Americas, WHO launched its global polio eradication initiative in 1988, aimed at ridding the world of polio by the year 2000. Globally, polio incidence has plummeted by almost 90 percent since that time, with the estimated number of cases dropping from 350,000 cases in 1988 to some 35,000 cases in 1997. Fifty-three countries remain endemic for polio.

A total of $1 billion will be needed between 1998 and 2005 to complete the polio eradication campaign. The United States, Japan, the United Kingdom, Germany, Denmark, Australia and Canada are major financial contributors. The U.S. Government contributes both technical support and about $72 million per year through the Agency for International Development and the Centers for Disease Control and Prevention.

The Initiative’s largest non-government supporters has been Rotary International, which launched a 20-year campaign in 1985 to vaccinate every child in the world against polio. By the year 2005, Rotary will have committed more than $400 million toward polio eradication and millions of hours of volunteer service by Rotary club members around the world.

Polio once caused widespread panic, also in industrialized countries, because infection occurred between apparently healthy people, especially children, and the symptoms could appear and kill a child on the same day, with no warning. Memories persist of hospital wards filled with the most severely afflicted children being kept alive in iron lungs, because their breathing muscles were paralyzed.

Without polio vaccine, the disease today would be killing or paralyzing about 550,000 people worldwide each year.

Polio eradication became possible because of the development of effective vaccines, especially the live oral polio vaccine developed in the early 1960s by Dr. Albert Sabin. Eradication is also feasible because the virus that causes polio affects only humans, vaccine immunity is lifelong, and there are no long-lasting environmental sources of the wild poliovirus.

The polio eradication initiative was inspired by the most successful public health program of all time, the global smallpox eradication initiative. When the global smallpox eradication program was established in 1967, there were 10-15 million cases of smallpox per year, causing at least 2 million deaths annually and 100,000 cases of blindness every year. The last case came in Somalia in 1977.

The global polio campaign has been focused on enlisting countries to carry out National Immunization Days (NIDs), in which national health programs seek to vaccinate every single child under the age of five against polio within a limited period, often on a single day.

At the beginning of 1998, 111 countries had undertaken at least one round of National Immunization Days. NIDs have now been conducted by all the polio endemic countries of Europe and Asia, as well as most polio endemic countries in Africa.

All four of the polio endemic countries that have not conducted full NIDs are in Africa — Sierra Leone, Liberia, the Democratic Republic of Congo and Somalia. Nigeria and Sudan also present major challenges in Africa. Afghanistan, Bangladesh, India and Pakistan are the most heavily affected countries in Asia.

“The conditions in Africa are proving to be especially difficult because of wars, civil unrest and poor infrastructure,” says Dr. Hull. “The final fight against polio may take place in Africa, but no country is free of polio until every country is free of polio, especially since an airline passenger could bring the disease to any nation on earth within 24 hours.”

This is the reason why every U.S. child must still be vaccinated against polio, even though the United States has not experienced a case since 1979. A sect in the Netherlands, which does not believe in vaccination, experienced an outbreak in that country in 1978, which then jumped to Canada, and then into the United States. A similar outbreak occurred in the Netherlands in 1992 and again jumped to Canada, but did not enter the U.S.

In 1997, the campaign in Africa succeeded in vaccinating 85 million children in 36 sub-Saharan countries, but the total population under the age of five is 120 million in that continent. NIDs must be conducted each year aiming to reach all the children of Africa for at least the next 3 years. One problem is that most of the financing for Africa will have to come from external sources. An estimated $80-90 million yearly will be needed in Africa. The initiative must also contend with deserts, reaching nomadic populations and working in countries where all vaccinations of children have been disrupted in recent years.

Rotary has, over the years, directed more than $100 million in grants to Africa, one quarter of its global commitment. In addition, Rotary International donated $400,000 this March in emergency assistance to a campaign of the Global Polio Eradication Initiative in southern Sudan to airlift polio vaccine for 600,000 children, which was organized by Operation Lifeline Sudan, for which UNICEF is the lead agency. Previous immunization attempts failed to reached a majority of children in southern Sudan due to floods, drought and an ongoing civil war.

The WHO plan of action for polio eradication outlines four basic strategies to achieve eradication:

  1. Routine immunization of infants — Every child born should receive 3 doses of oral polio vaccine (OPV) during the first year of life as part of the series of immunizations to protect children against six major killers of children: measles, whooping cough, tetanus, diphtheria, tuberculosis and polio. WHO recommends that countries immunize at least 90 percent of infants with all vaccines, paying particular attention to minorities and other under-served populations. High levels of routine coverage reduce disease to low immunization levels and make eradication feasible.
  2. National immunization days (NIDs) — During national immunization days, all children less than 5 years of age are immunized with 2 additional doses of OPV, spaced about one month apart. These mass campaigns boost the immunity of children to the point that spread of polio virus from child to child is no longer possible and the circulation of the virus stops.
  3. Acute Flaccid Paralysis (AFP) surveillance — Because the vast majority of poliovirus infections do not result in paralysis and other diseases can be mistaken for polio, a system must be established to detect every possible case of polio and collect and test specimens in a laboratory of certified competence. This will allow epidemiologists to identify the populations where polio virus transmission persists.
  4. Mopping-up immunization — In the final stages of eradication, polio will be limited to a few geographic areas, typically areas where health infrastructure is poor and immunization services inadequate. Surveillance data are used to identify these areas and target them for door-to-door “mopping-up” immunization campaigns.

The surveillance system necessary to track circulation of wild polioviruses and to eventually certify the eradication of polio has been established in most polio endemic countries and is being rapidly improved. A global laboratory network of 87 laboratories has been established to oversee the surveillance system. The major suppliers of laboratory equipment have been the Japanese Government, Rotary and WHO. Much of the training has been conducted by the Dutch National Public Health Laboratory and the U.S. Centers for Disease Control.

A total of 142 countries have started Acute Flaccid Paralysis (AFP) surveillance systems, 46 of which currently meet the AFP standard of 1/100,000 (on average, one in every 100,000 children is paralyzed from all causes. If a country’s polio surveillance system therefore fails to find this percentage of paralyzed children, the Initiative presumes its system is not working correctly). There are eight polio endemic countries that have not yet begun AFP surveillance on a national scale. Some countries such as the United States and some Western European nations have been free of polio for many years and do not use the AFP surveillance system.

The performance standards for surveillance are being achieved in the WHO Regions where AFP surveillance has been established for several years. In the African and Southeast Asian Regions, the surveillance is in the early stages of being established. Additional support is needed to rapidly bring surveillance to the necessary standard to stop wild poliovirus transmission.

Political turmoil and civil war are probably the most serious challenges to the eradication initiative. The most prominent example today is Democratic Republic of the Congo (DRC), the former Zaire, where political and social instability over a period of years has caused a major deterioration in the country’s infrastructure and health care system. The DRC plans to conduct its first National Immunization Day during 1998. Other countries facing political unrest and civil war include Afghanistan, Angola, Liberia, Somalia and Sudan.

Truces have been declared for polio eradication, most recently in Afghanistan, where more than 3.5 million children under the age of five were vaccinated against polio in April and May in 1997. Another April-May truce is also scheduled for this year.

The common factor in recent polio outbreaks — epidemics in India (1997), Albania (1996), Pakistan (1995 and 1997), Sudan (1993) and Zaire (1995) — is a failure to immunize. The size of the non-immunized group can range from a small isolated group that refuses vaccine on religious or cultural grounds, to all children born around the same time in countries lacking vaccines.

In some of the poorest countries, low immunization coverage is often due to poor health infrastructure development and a failure to reach the majority of the population with basic health services.

Egypt and Pakistan — traditionally major reservoirs of polio stemming from their large and dense populations — have had especially difficult tasks. Four or more years of NIDs have been conducted in both of these countries. Egypt radically reduced its problem, reporting just 14 cases in 1997. Pakistan, with a larger polio problem is making a major commitment to revitalize its entire immunization program and has just finished its most successful NID in February.

Immunization coverage is not equal in all areas of the world. There are 14 countries in the world in which polio immunization coverage of children has not yet reached 50 percent, with 12 of those countries in sub-Sahara Africa.

However, even in Africa, progress is being made; routine immunization coverage for WHO’s African Region exceeded 50 percent for the first time in 1994.

The WHO report also warns of the need to improve the quality of disease surveillance in many countries, especially Africa. Even some countries with high levels of immunization have inadequate epidemiological surveillance systems.

Polio-free countries in the Western hemisphere and Europe face a totally different challenge. As years pass without domestic or imported cases of polio, a tendency exists to relax surveillance and immunization coverage.

“We have seen repeated outbreaks of polio in Europe from viruses imported into population groups with low immunization coverage, says Jong-Wok Lee, MD, Director of the WHO Global Programme for Vaccines and Immunization. “Unless we are vigilant, the virus will be back again in other industrialized countries.”

Once the wild polio virus is eradicated and immunization can be stopped worldwide, the global community will save $1.5 billion yearly.

NIDs (National Immunization Days) have been the motivation for a number of remarkable displays of international cooperation. In Operation MECACAR (Middle East, Caucasus and Central Asian Republics), first conducted in 1995, 19 countries in the Middle East, the Caucasus and the Central Asia Republics coordinated their NIDs, to stop wild polio virus transmission in Southwestern and Central Asia. The campaign immunized 56 million children in the first Operation MECACAR. Russia joined MECACAR in 1996.

In December, 1996, seven South Asian nations — Bangladesh, Bhutan, India, Myanmar, Nepal, Pakistan and Thailand — coordinated their NIDs in the first week of December, immunizing approximately 181 million children.

India was able to immunize 127 million children in January of 1997 and 134 million in January of this year. China conducted a sub-national immunization campaign at the same time, immunizing 50 million children. As a result of such campaigns, the number of reported polio cases has dropped dramatically in India from 24,257 in 1988 to 1,555 in 1997, and from 667 in China in 1988 to 0 in 1997.

How Polio Attacks

Polio can strike at any age but affects mainly children under the age of 3 years — 50-70 percent of all cases. The virus usually enters a victim through the mouth and then multiplies inside the throat and intestines.

The incubation period ranges from 4-35 days and the initial symptoms include fever, fatigue, headache, vomiting, constipation, stiffness in the neck, and pain in the limbs. Once established, polio can enter the bloodstream and invade the central nervous system, spreading along nerve fibers. As the virus multiplies, it destroys the motor neurons (complete nerve cells that specialize as conductors of impulses) that activate muscles. These destroyed nerve cells cannot be regenerated and the affected muscles no longer function. Muscle pain, spasms and fever are associated with the rapid onset of acute flaccid (floppy) paralysis.

Polio paralysis is almost always irreversible. The muscles of the legs are affected more often than the arm muscles. More extensive paralysis, involving the trunk and muscles of the thorax and abdomen, can result in quadriplegia. In the most severe cases, poliovirus attacks the motor neurons of the brain stem — reducing breathing capacity and causing difficulty in swallowing and speaking, known as “bulbar polio.” Without adequate respiratory support, bulbar polio can result in death by asphyxiation.

Less than 1 percent of polio infections result in paralysis. As many as 90 percent of cases produce no, or very mild, symptoms and usually go unrecognized. The remaining cases, known as “abortive polio,” involve mild flu-like symptoms common to other viral infections — mild fever, sore throat, abdominal pain and vomiting. Some 5-10 percent of all polio infections result in aseptic meningitis, a viral inflammation of the outer covering of the brain.

The problem is that most people infected with poliovirus are never aware of it, but they can spread poliovirus in close contacts. The virus is shed intermittently in feces for several weeks, which enables the rapid spread, especially in areas where hygiene and sanitation are poor, but also in any environment where young children not yet fully toilet-trained.

Polio can also be spread when food or drink is contaminated by feces. Evidence also exists that flies can passively transfer poliovirus from feces to food.

Poliovirus circulates “silently” at first, possibly infecting up to 200 people before the first case of polio paralysis emerges. Because of this silent transmission and the rapid spread of poliovirus, WHO considers a single confirmed case of polio paralysis to be evidence of an outbreak, particularly in countries where very few cases are occurring and the disease is close to being eradicated.

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