Disease Eradication

 by Isabel Hookway

Polio drops (Unicef)

When a disease stops circulating in an area, it is considered eliminated. When a disease stops circulating globally, it is considered eradicated. So far, only two diseases have been eradicated, smallpox and rinderpest. There are now global efforts to eradicate poliovirus.  For a disease to be considered eradicable, it needs to meet certain criteria. It needs to be an infectious disease, humans need to be the major host of the disease, and there must be effective vaccines or treatments for the disease.

Smallpox was the first disease to be eradicated. Smallpox was an infectious disease that caused epidemics throughout history. It resulted in 300 million deaths throughout the 20th century. On average, 30% of people who got smallpox died from it. The last recorded case of smallpox occurred in Somalia in 1977, and the disease was declared eradicated in 1980 by the World Health Organisation. In 1959, the WHO started a plan to rid the world of smallpox. But, due to a lack of funding and a shortage of vaccine donations, the scheme failed. In 1967, the WHO relaunched the program as the intensified smallpox eradication program - or the ISEP. Smallpox was a good candidate for eradication due to the fact it was highly visible. Patients developed an easily recognisable rash, meaning they could be treated and isolated quickly. Also, the time from exposure to the initial symptoms developing was short. The eradication was completed by close monitoring and ring vaccination. Ring vaccination is where anyone who could have been in contact with the patient is vaccinated. This was effective as the vaccine worked quickly. Many people now consider the eradication of smallpox to be the biggest achievement in international public health.

Rinderpest was a disease caused by the rinderpest virus and it affected cattle and buffalo. It is closely related to the human measles virus, and infected animals suffer from symptoms such as a fever, wounds in the mouth, and diarrhoea. The virus spread via droplets so that animals got infected by inhaling sick animals’ breath, secretions or excretions. The death rate was extremely high, up to 100% in certain herds. Rinderpest did not only affect animals but humans as well, as it severely affected their livelihoods. Rinderpest outbreaks were responsible for famines that caused millions of deaths.

The outbreak of the disease in Europe in the 1920s was controlled by the restriction of cattle movement, immediate slaughter and vaccination. From this outbreak, the office international des epizootics (OIE) was formed and is now known as the world organization for animal health. Before a vaccine was developed, improved hygiene, slaughter and quarantine were all effective in controlling the rate of movement of the virus. In 1960, the English veterinary scientist Walter Plowright developed an inactivated vaccine. Plowright was awarded the world food prize in 1999, for making rinderpest’s “eradication, for the first time in human history, a practical objective”. The last case of rinderpest was recorded in Mauritania in 2003 and was declared eradicated by the OIE on May 25th, 2011.

Polio is an infectious disease that can travel to a person's spinal cord, and cause permanent paralysis, usually spread through dirty water. In about 98% of cases, polio is a mild illness, with no symptoms or mild viral-like symptoms. In 1988, when the disease was present in 125 counties, 350000 people were paralysed each year. The Global Polio Eradication Initiative (GPEI) was launched in 1988. The strategy focuses on national campaigns and local campaigns in the highest risk countries to provide all children with multiple doses of oral vaccination. Some of these efforts include door to door vaccinations where a known or suspected case occurs. Other door to door efforts include areas that risk reimportation, limited access to healthcare, a high population density, and poor sanitation.  The global number of polio cases has declined by more than 99.9% worldwide since the launch of the GPEI. Because of the widespread vaccination, polio was eliminated from the western hemisphere in 1994. It now only continues to circulate in just two countries, Afghanistan and Pakistan. Rigorous vaccination efforts take place in these countries to eliminate these last two pockets of disease.

The GPEI also monitors poliovirus to control outbreaks. This is particularly difficult because only 1-2% of infections result in paralytic disease, and confirming the disease requires analysis of stool specimens. Through research conducted by the GPEI, new and improved surveillance has been implemented: testing sewage water samples for any traces of the poliovirus in the community. 

The immediate benefits of disease eradication are obvious - saving lives and preventing suffering globally. Failure to eradicate polio could lead to over 200,000 cases annually, with 1 in 200 leading to irreversible paralysis. But saving lives is not the only benefit of disease eradication. There are major economic benefits that go along with this. Controlling disease is cheaper than the continued burden on the healthcare system, and the lost productivity of a sick population. Experts have said that eradicating polio would generate US$14 billion in cumulative cost savings by 2050 when compared with the cost of controlling the virus indefinitely.