In theory, if the right tools were available, it would be possible to eradicate all infectious diseases. In reality there are distinct biological features of the organisms and technical factors of dealing with them that make their potential eradicability more or less likely. Three indicators however, are considered of primary importance in determining the likelihood of successful eradication: That effective interventional tools are available to interrupt transmission of the agent, such as a vaccine. That diagnostic tools, with sufficient sensitivity and specificity, be available to detect infections that can lead to transmission of the disease, and that humans are required for the life-cycle of the agent, which has no other vertebrate reservoir and cannot amplify in the environment.
When many hosts are vaccinated, especially simultaneously, the transmission of wild virus is blocked, and the virus is unable to find another susceptible individual to infect. Because poliovirus can only survive for a short time in the environment (a few weeks at room temperature, and a few months between 0–8° Celsius (32–46° Fahrenheit)) without a human host the virus dies out.
Herd immunity is an important supplement to vaccination. Among those individuals who receive oral polio vaccine, only 95 percent will develop immunity. That means 5 of every 100 given the vaccine won’t develop any immunity and will be susceptible to developing polio. According to the concepts of herd immunity this population whom the vaccine fails, are still protected by the immunity of those around them. Herd immunity can only be achieved when vaccination levels are high. It is estimated that 80-86 percent of individuals in a population must be immune to polio for the susceptible individuals to be protected by herd immunity. If routine immunization were stopped, the number of unvaccinated, susceptible individuals would soon exceed the capability of herd immunity to protect them.
|International Polio Cases by Year|
Following the widespread use of poliovirus vaccine in the mid-1950s, the incidence of poliomyelitis declined rapidly in many industrialized countries. Czechoslovakia became the first country in the world to scientifically demonstrate nationwide eradication of poliomyelitis in 1960. In 1962 — just one year after Sabin's oral polio vaccine (OPV) was licensed in most industrialized countries — Cuba began using the oral vaccine in a series of nationwide polio campaigns. The early success of these mass vaccination campaigns suggested that polioviruses could be globally eradicated. The Pan American Health Organization (PAHO), under the leadership of Ciro de Quadros, launched an initiative to eradicate polio from the Americas in 1985.
In 1994 the Indian Government launched the Pulse Polio Campaign to eliminate polio. The current campaign involves annual vaccination of all children under age five. Most families have allowed their children to take the vaccine.
In 1995 Operation Mecacar (Mediterranean, Caucasus, Central Asian Republics and Russia) were launched; National Immunization Days were coordinated in 19 European and Mediterranean countries. In 1998, Melik Minas of Turkey became the last case of polio reported in Europe. In 1997 Mum Chanty of Cambodia became the last person to contract polio in the Indo-West Pacific region. In 2000 the Western Pacific Region (including China) was certified Polio-free.
In October 1999, the last isolation of type 2 poliovirus occurred in India. This type of poliovirus appears to have been eradicated.
In 2002, an outbreak of polio in India occurred after the number of planned polio vaccination campaigns was reduced and the state of Uttar Pradesh accounted for nearly two-thirds of total worldwide cases reported. (See Poliokarte-Dezember-2002.jpg.)
In the Kano province in Northern Nigeria, which operates under Sharia (Muslim religious law), the immunization campaign was suspended in September 2003 when prominent Muslim leaders claimed vaccines supplied by Western donors were adulterated to reduce fertility and spread HIV as part of a U.S.-led drive against Islam. On June 30, 2004, after a 10-month ban on polio vaccinations, the WHO announced that Kano had pledged to restart the campaign in early July. During the ban the virus spread across Nigeria and into 12 neighboring countries that had previously been polio-free. By 2006, this ban would be blamed for 1,500 children being paralyzed and having caused $450 million for emergency activities. In addition to the rumors of sterility and the ban by Nigeria's Kano state, civil war and internal strife in the Sudan and Ivory Coast have complicated WHO's polio eradication goal. In 2004, almost two-thirds all the polio cases in the world occurred in Nigeria (760 out of 1170 total).
| Chad, Eritrea,|
Nigeria experienced a drop in the number of polio cases of nearly a half from last year, according to the World Health Organization. Officials credit the drop in new infections to improved political control in the southern states and resumed immunisation in the north, where Muslim clerics led a boycott of vaccination in late 2003. Local governments and clerics allowed vaccinations to resume on the condition that the vaccines be manufactured in Indonesia, a majority Muslim country, and not in the United States.
Eradication efforts in the Indian sub-continent have met with a large measure of success. Using the Pulse Polio campaign to increase polio immunization rates, India recorded just 66 cases in 2005; down from 135 cases reported in 2004, 225 in 2003, and 1,600 in 2002.
Yemen, Indonesia and Sudan, countries which had been declared polio-free since before 2000, each reported hundreds of cases - probably imported from Nigeria. On May 5 2005, news reports broke that a new case of polio was diagnosed in Java, Indonesia and the virus strain was suspected to be the same as the one that has caused outbreaks in Nigeria. New public fears over the safety, which were unfounded, impeded vaccination efforts in Indonesia. In summer 2005 the WHO, UNICEF and the Indonesian government made new efforts to lay the fears to rest, recruiting celebrities and religious leaders in a publicity campaign to promote vaccination.
The first case of the polio outbreak in Sudan was detected in May 2004. The reemergence of polio led to stepped up vaccination campaigns. In the city of Darfur; 78,654 children were immunized and 20,432 more in southern Sudan (Yirol and Chelkou).
In the United States it was reported that "on September 29, 2005 the Minnesota Department of Health (MDH) identified poliovirus type 1 in an unvaccinated, immunocompromised infant girl aged 7 months (the index patient) in an Amish community whose members predominantly were unvaccinated for polio. The patient has no paralysis; the source of the patient's infection is unknown. Subsequently, poliovirus infections in three other children within the index patient's community have been documented."
In 2007 there were 1,307 cases of poliomyelitis reported worldwide. Over 60% of cases (866) occurred in India; while in Nigeria, the number of polio cases fell dramatically, from 1,122 cases reported in 2006 to 285 cases in 2007. Turai Yar'Adua, wife of recently-elected Nigerian president Umaru Yar'Adua, made the eradication of polio one of her priorities. Attending the launch of immunization campaigns in Birnin Kebbi in July 2007, the First Lady urged parents to vaccinate their children and stressed the safety of oral polio vaccine.
Pakistan and Afghanistan reported 32 and 17 cases respectively in 2007. In Pakistan's tribal areas, immunization campaigns were hindered by Muslim clerics who claim that immunizations are part of an American conspiracy designed to sterilize the local Muslim population. In February 2007, physician Abdul Ghani, who was in charge of polio immunizations in a key area of disease occurrence in northern Pakistan, was killed in a terrorist bombing. In July 2007, a student traveling from Pakistan imported the first polio case to Australia in over 20 years. Other countries with significant numbers of wild polio virus cases include the Democratic Republic of the Congo which reported 41 cases, Chad with 11 cases, and Niger and Myanmar, each of which reported 11 cases.