Smallpox eradication

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview[edit | edit source]

Smallpox was declared eradicated in 1980 by the WHO. The eradication of smallpox required a global effort. Since every country was susceptible of the devastating disease, eradicating this infection was expensive and took many years.

Eradication[edit | edit source]

Since Jenner demonstrated the effectiveness of cowpox to protect humans from smallpox circa 1796, various attempts were made to eliminate smallpox. In 1842, England banned inoculation, later progressing to mandatory vaccination instead. In the United States, from 1843 to 1855 first Massachusetts, and then other states required vaccination. Although some disliked these measures, coordinated efforts against smallpox went on, and the disease continued to diminish in the wealthy countries. In poorer countries, vaccines and the necessary infrastructure were less affordable and available.

In 1958 the Soviet Union called for the eradication of smallpox from the planet. At that point, 2 million people were dying every year. In 1967, an international team was formed under the leadership of an American, Donald Henderson. To eradicate smallpox, each outbreak had to be stopped from spreading, by isolation of cases and vaccination of everyone who lived close by. This process is known as ring vaccination. The key to this strategy was surveillance and containment. Surveillance can be best defined as the monitoring of cases in a community. The initial problem the WHO team faced was inadequate reporting of smallpox cases, as many cases did not come to the attention of the authorities.

The fact that man is the only reservoir for smallpox infection played a significant role in WHO deciding to eradicate smallpox. There are many other pox viruses in nature, including monkeypox. However, none appears to be of public health significance. In addition, smallpox carriers did not exist.

WHO established a network of consultants who assisted countries in setting up surveillance and containment activities.

Eradicating smallpox required huge effort and concentration of manpower. In India and Bangladesh, religion and civil strife along with natural disasters became obstacles. In fear of offending the goddess associated with the disease, many Hindus refused the vaccine. In some countries, such as the Sudan, civil war threatened to interfere with eradication attempts. Clearly, health teams placed themselves in great danger by working in war-torn areas. Surprisingly, none of the team members were hurt in the process.

Natural events also impeded the vaccination team’s efforts. The monsoon rains burst dams and dikes. The rain and flooding forced people to flee, once again allowing smallpox to spread. This outbreak took the team a whole year to stop.

The last major European outbreak of smallpox was the 1972 outbreak of smallpox in Yugoslavia. After a pilgrim from Kosovo returned from the Middle East, where he had contracted the virus, an epidemic infected 175 people, causing 35 deaths. Authorities declared martial law, enforced quarantine, and undertook massive revaccination of the population, enlisting the help of the WHO and Donald Henderson. In two months, the outbreak was over. Prior to this, there had been a smallpox outbreak in May-July of 1963 in Stockholm, Sweden, brought from the Far East by a Swedish sailor; this had been dealt with by quarantine measures and vaccination of local population.^[2]

The last naturally occurring case of Variola Minor was diagnosed in Somalia on a cook named Ali Maow Maalin on October 26, 1977. The last naturally occurring case of the more deadly Variola Major had been detected in October 1975 in a two-year-old Bangladesh girl, Rahima Banu. In the final tally, the U.S. had applied $300 million to the eradication program.

The global eradication of smallpox was certified, based on intense verification activities in countries, by a commission of eminent scientists in December 1979 and subsequently endorsed by the World Health Assembly in 1980.^[3]

Since Jenner demonstrated the effectiveness of cowpox to protect humans from smallpox in 1796, various attempts were made to eliminate smallpox on a regional scale. As early as 1803, the Spanish Crown organized a mission (the Balmis Expedition) to transport the vaccine to the Spanish colonies in the Americas and the Philippines, and establish mass vaccination programs there. The US Congress passed the Vaccine Act of 1813 to ensure that safe smallpox vaccine would be available to the American public. By about 1817, a very solid state vaccination program existed in the Dutch East Indies. In British India a program was launched to propagate smallpox vaccination through Indian vaccinators, under the supervision of European officials. Nevertheless, British vaccination efforts in India, and in Burma in particular, were hampered by stubborn indigenous preference for inoculation and distrust of vaccination despite tough legislation, improvements in the local efficacy of the vaccine and vaccine preservative, and education efforts^[4]. By 1832, the federal government of the United States established a smallpox vaccination program for Native Americans^[5]. In 1842, the United Kingdom banned inoculation, later progressing to mandatory vaccination. The British government introduced compulsory smallpox vaccination by an Act of Parliament in 1853. In the United States, from 1843 to 1855 first Massachusetts, and then other states required smallpox vaccination. Although some disliked these measures,^[6] coordinated efforts against smallpox went on, and the disease continued to diminish in the wealthy countries. By 1897, smallpox had largely been eliminated from the United States^[7]. In Northern Europe a number of countries had eliminated smallpox by 1900, and by 1914, the incidence in most industrialized countries had decreased to comparatively low levels. Vaccination continued in industrialized countries, until the mid to late 1970s as protection against reintroduction. Australia and New Zealand are two notable exceptions; neither experienced endemic smallpox and never vaccinated widely, relying instead on protection by distance and strict quarantines^[8].

The first hemisphere-wide effort to eradicate smallpox was made in 1950 by the Pan American Health Organization^[9]. The campaign was successful in eliminating smallpox from all American countries except Argentina, Brazil, Colombia, and Ecuador^[8]. In 1958 Professor Viktor Zhdanov, Deputy Minister of Health for the USSR, called on the World Health Assembly to undertake a global initiative to eradicate smallpox. The proposal (Resolution WHA11.54) was accepted in 1959^[10]. At this point, 2 million people were dying from smallpox every year. Overall, however, the progress towards eradication was disappointing, especially in Africa and in the Indian subcontinent. In 1966 an international team, the Smallpox Eradication Unit, was formed under the leadership of an American, Donald Henderson^[10]. In 1967, the World Health Organization intensified the global smallpox eradication by contributing $2.4 million annually to the effort.

In the early 1950s an estimated 50 million cases of smallpox occurred in the world each year. To eradicate smallpox, each outbreak had to be stopped from spreading, by isolation of cases and vaccination of everyone who lived close by. This process is known as "ring vaccination". The key to this strategy was monitoring of cases in a community (known as surveillance) and containment. The initial problem the WHO team faced was inadequate reporting of smallpox cases, as many cases did not come to the attention of the authorities. The fact that humans are the only reservoir for smallpox infection, and that carriers did not exist, played a significant role in the eradication of smallpox. The WHO established a network of consultants who assisted countries in setting up surveillance and containment activities. Early on donations of vaccine were provided primarily by the Soviet Union and the United States, but by 1973, more than 80% of all vaccine was produced in developing countries^[8].

The last major European outbreak of smallpox was in 1972 in Yugoslavia, after a pilgrim from Kosovo returned from the Middle East, where he had contracted the virus. The epidemic infected 175 people, causing 35 deaths. Authorities declared martial law, enforced quarantine, and undertook widespread re-vaccination of the population, enlisting the help of the WHO. In two months, the outbreak was over^[11]. Prior to this, there had been a smallpox outbreak in May–July 1963 in Stockholm Sweden, brought from the Far East by a Swedish sailor; this had been dealt with by quarantine measures and vaccination of the local population.

By the end of 1975, smallpox persisted only in the Horn of Africa. Conditions were very difficult in Ethiopia and Somalia, where there were few roads. Civil war, famine, and refugees made the task even more difficult. An intensive surveillance and containment and vaccination program was undertaken in these countries in early and mid-1977, under the direction of Australian microbiologist Frank Fenner. As the campaign neared its goal, Fenner and his team played an important role in verifying eradication^[12]. The last naturally occurring case of indigenous smallpox (Variola minor) was diagnosed in Ali Maow Maalin, a hospital cook in Merca, Somalia, on 26 October 1977^[13]. The last naturally occurring case of the more deadly Variola major had been detected in October 1975 in a two-year-old Bangladeshi girl, Rahima Banu^[14].

References[edit | edit source]

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