4. Responsible for the death of American President William Henry Harrison just thirty-two days into his term of office, typhoid fever continues to afflict humanity due to poor hygiene and opposition to vaccinations
Typhoid fever, taking between six and thirty days after infection to indicate symptoms, is a bacterial infection caused by a strain of salmonella. Spread by eating food or drinking fluids contaminated with infected feces, the condition causes extreme fevers, abdominal pain, headaches, rashes, vomiting, and constipation. Without appropriate treatment, typhoid is capable of lasting for months and carries a mortality rate as high as 20 percent. First identified in the 19th century, in 1896 an early vaccination was introduced in Great Britain to combat the prevalence of the infection in soldiers fighting the Boer War in South Africa.
Today, vaccinations are capable of preventing contraction for up to seven years and, in conjunction with concurrent improvements in public sanitation and hygiene, the 20th century saw a marked decline in instances of typhoid in the developed world. However, typhoid remains at large in the developing world, particularly India. In 2015, an estimated 12.5 million new cases were diagnosed worldwide, resulting in approximately 149,000 deaths. Modern modes of travel and exposure to these infected regions have reintroduced typhoid to the developed world, with roughly 400 cases identified in the United States each year including an outbreak in Oklahoma in 2015.