Disease Elimination vs. Eradication

Childhood Infection Basics

The Carter Center has worked to help eradicate Guinea worm disease.
Former U.S. President Jimmy Carter talking to Ghanaian children about Guinea worm disease. Photo by Louise Gubb/The Carter Center

News that rubella has been eliminated in the Americas has a lot of people misusing the terms elimination and eradication again.

Disease Eradication

Of course, eradication is the goal of most immunization programs.

Once a vaccine-preventable disease is eradicated, the worldwide incidence of the disease is reduced to zero so that intervention, including immunizations, are no longer needed.

So far, small pox is the only disease that has been eradicated.

The Thirty-Third World Health Assembly declared that smallpox was eradicated in 1979. Many more diseases have been brought under control with vaccines, including diphtheria, measles, polio, tetanus, whooping cough, and yellow fever.

And both measles and polio have been targeted for eradication.

Disease Elimination

Similar to eradication, when a disease is eliminated, the incidence of disease is reduced to zero, but only in a particular geographic area. Unlike eradication, since the disease is still around in other areas, interventions must continue so that the disease doesn't come back in that area.

To be more clear, when an epidemiologist says that a disease is eliminated in an area, what they are really saying is that the endemic form of the disease has been eliminated - someone has to reintroduce the disease from outside the area for outbreaks to occur. So you can still have cases and even big outbreaks like we continue to see with measles in the United States, however, they always start with someone who initially got infected from outside the country.

In the United States:

  • endemic yellow fever (1905) and malaria (1951), both spread by mosquito bites, were the first diseases to be eliminated
  • endemic polio was declared eliminated in 1979
  • endemic measles was declared eliminated in 2000
  • neonatal tetanus was declared eliminated before 2000
  • endemic rubella and congenital rubella syndrome were declared eliminated in 2004
  • endemic respiratory diphtheria was declared eliminated in 2009 and the last big outbreak was in the 1970s

Again, even though these diseases have been eliminated in the United States, that doesn't mean that you can't get them anymore. If you are not vaccinated or have a problem with your immune system and travel to an area of the world where these diseases are still common, you are at risk to get sick and bring that disease home with you, infecting others.

Disease Control

Unfortunately, not all diseases can be eliminated and eradicated.

This may have nothing to do with how well a vaccine works or whether or not people get their kids vaccinated though.

In some cases, an infection might not be contagious and is simply found in the environment, like Ascariasis (roundworms) or tetanus. To eradicate tetanus, we would have to get rid of the tetanus bacteria at its source - soil.

Other reasons that a disease might not be able to be easily eliminated or eradicated could include that:

  • it can also infect animals - rabies, yellow fever, Chagas’ disease
  • the disease causes infections without symptoms - Amebiasis
  • the presence of asymptomatic carriers - diphtheria
  • natural infection doesn't provide life-long immunity - malaria
  • the disease doesn't always have obvious symptoms - polio
  • people are contagious before they have obvious symptoms - measles

Hopefully, these challenges will soon be overcome for more diseases, though, especially vaccine-preventable diseases like polio and measles.

Goals for Global Elimination and Eradication of Diseases

Tragically, we have a long history of not meeting our goals for disease elimination and eradication.

Still, a lot of progress has been made over the years, millions of lives have been saved, and many more deaths will be prevented if we meet our current goals to eradicate or eliminate these diseases:

  • polio - since the initial war on polio was started by President Franklin D Roosevelt in 1938 and the development of the first polio vaccines in the 1950s to the creation of The Global Polio Eradication Initiative in 1988, eradicating polio has been a priority for health experts. Unfortunately, we missed the first goal of eradicating polio by 2000, but are certainly getting close, as only three countries still have endemic polio - Afghanistan, Nigeria and Pakistan - and worldwide cases are at all time lows. The new goal is to have a polio-free world by 2018!
  • measles - We have missed a lot of the goals on the way to eradicating measles, including the goal to eliminate measles in the United States by 1982 (wasn't met until 2000), the goal of global eradication of measles by 2010 which was first set in 1996, and the goal of reducing global measles mortality by 90% by 2010 over 2000 levels (there was a 74% decrease though!). We will hopefully meet the latest goals of reducing global measles mortality by 95% by 2015 over 2000 levels, eliminating measles in at least five WHO regions by 2020, and setting a target date for measles eradication by the end of 2015.
  • maternal and neonatal tetanus - while many people associate tetanus with stepping on a rusty nail, tetanus can also affect mothers and their newborn babies, especially when hygienic practices aren't available when the baby is delivered or when they care for the baby's umbilical cord. Although the target dates have been postponed from the initial goals of 1995, 2000, 2005 and 2015, eliminating maternal and neonatal tetanus is still a goal. Considering that at least 49,000 newborns died of neonatal tetanus as late as 2013, which is down from 787,000 in 1988, significant progress continues to be made.
  • Guinea worm disease - although not usually life-threatening, Guinea worm disease is still a serious disease that causes suffering for those who become infected with the Guinea worm larvae that can grow to become adults that are 2 to 3 feet long. Fortunately, Guinea worm disease should be the next disease that is eradicated, with cases at an all time low thanks to the efforts of The Carter Center.
  • lymphatic filariasis (Elephantiasis) - transmitted by infected mosquitoes, lymphatic filariasis is another disabling condition that has been targeted for elimination using insecticidal bed nets and drugs donated by Merck and GlaxoSmithKline, hopefully by 2020.
  • taeniasis/cysticercosis (tapeworms) - eating undercooked pork that is infected with larval cysts of the tapeworm Taenia solium can cause intestinal tapeworms (taeniasis). Swallowing the eggs of these intestinal tapeworms (located in an infected persons feces) can lead to getting cysticercosis, in which the larval cysts can infect brain (neurocysticercosis) and muscle tissue, etc. Although thought to be potentially eradicable, cysticercosis is considered to be of several major neglected tropical diseases.
  • mumps - a vaccine-preventable disease that is thought to be potentially eradicable.
  • leprosy - using expanded multi-drug therapy regimens, leprosy is now in the final push phase of elimination.
  • river blindness (onchocerciasis) - a parasitic infection that is spread through the bite of small black flies, river blindness is targeted for eliminated in select regions using a drug donated by Merck.
  • trachoma - another eye infection that is spread by flies and which can lead to blindness, blinding trachoma is targeted for global elimination by 2020. In addition to health education and corrective eye surgeries, the effort has been aided by Pfizer donating an antibiotic to fight trachoma.
  • rubella - rubella is also targeted for elimination from at least five WHO regions by 2020.

Unfortunately, even as we make progress to control, eliminate, and eradicate these diseases, some are beginning to make a comeback.

And no, it is not just because of parents choosing to intentionally not vaccinate their children. In many parts of the world, in addition to the humanitarian crisis and health challenges posed by natural disasters, children are getting sick in war zones and refugee camps and simply can't be vaccinated.

Sources:

The Carter Center. Disease considered as candidates for global eradication by the International Task Force for Disease Eradication. Updated April 2008.

CDC. The Principles of Disease Elimination and Eradication. MMWR. December 31, 1999 / 48(SU01);23-7.

CDC. Manual for the Surveillance of Vaccine-Preventable Diseases. Accessed May 2015.

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