The surprising health risks and secrets behind kissing
Where and when: Budapest area from 1912 to 1916.
Kiss strangled his victims and drained their blood before placing them in barrels on his property. Kiss escaped and his fate remains a mystery.
Where and when: USA and Canada in 1926 and 1927.
Also known as "Gorilla Killer" or "the Dark Strangler," he targeted boardinghouse landladies.
Where and when: Colombia from 1999 to 2003.
A child molester and serial killer known as "the Monster of the Cane Fields," he was an ice-cream vendor who lured his victims to cornfields.
Where and when: Louisiana from 1997 to 2006.
He targeted men in gay bars who were willing to have intimate relationships for money.
Where and when: Egypt from 1999 to 2006.
Also known as "al-Tourbini," the gang leader targeted homeless children, mostly boys, aboard trains.
Where and when: Angarsk, Irkutsk, and Vladivostok from 1992 to 2010.
Nicknamed "The Werewolf," he targeted women he considered immoral.
Where and when: Sutter County, California in 1971.
He targeted migrant farm workers and buried them in fruit orchards along the Feather River.
Where and when: Southeast Texas from 1968 to 1973.
Known as the "Candy Man," he assaulted and tortured young boys with the help of two teenaged accomplices, one of whom later killed Corll.
Where and when: Johannesburg area from 1996 to 1997.
Known as the "Wemmer Pan Killer," he used guns, rocks, a knife, and a hammer, and targeted victims of various types.
Where and when: committed crimes in modern-day Germany from 1900 to 1924.
Often regarded as "The Forgotten Cannibal," the Prussian criminal killed and cannibalized travelers and vagrants.
Where and when: South Africa from 1994 to 1995.
Known as South Africa's Ted Bundy, he lured unemployed women with job promises.
Where and when: Modern-day Iran and Iraq from 1907 to 1934.
Known as "Asghar the Murderer," he killed and assaulted his first victims at 14.
Where and when: Medan area from 1986 to 1997.
He strangled women and buried them up to their waists in a sugarcane plantation as part of a ritual, seeking magical powers.
Where and when: Ukraine from 1984 to 2005.
A former Ukrainian police officer, he killed girls before engaging in intimate acts postmortem.
Where and when: Moscow from 1992 to 2006.
Also known as the "Chessboard Killer," he used vodka to lure victims, mainly elderly homeless men. Many suspect he wanted to become the worst killer in Russian history.
Where and when: Goiás area from 2011 to 2014.
The security guard targeted women, homeless people, and gay men. He approached on motorcycle pretending to be an armed robber.
Where and when: Washington state from 1982 to 2000.
Also known as the "Green River Killer," the truck driver preyed on vulnerable women.
Where and when: Ukraine from 1989 to 1996.
He selected isolated houses and gained the occupants' attention by creating a commotion. He always killed the older male occupant first.
Where and when: Rostov area, Russia, from 1978 to 1990.
Known as "The Rostov Ripper," the former school teacher is notorious for mutilating his victims, often eating their sexual organs.
Where and when: Russia from 1921 to 1923.
Known as "The Wolf of Moscow," the horse trader invited clients into his home and gave them vodka before killing them.
Where and when: Anhui, Hebei, Henan, and Shandong between 2000 to 2003.
He entered victims' homes and killed all of the occupants with axes, hammers, and shovels. He always wore new clothes and large shoes.
Where and when: Ecuador, Colombia, and possibly Brazil from 1974 to 1986.
Because he preyed on virgins, the majority of his victims were children. Though he killed 72, he is said to have assaulted at least 150.
Victims: 138 confirmed, possibly over 300.
Where and when: Colombia, Ecuador, and Venezuela from 1992 to 1999.
Known as "The Beast," he more frequently preyed on homeless boys, luring them with money. He often tortured the victims severely before killing them.
See also: Notorious killers in American history
Where and when: Liaoning from 1995 to 2003.
He is regarded as one of the most notorious murderers and rapists in Chinese history.
Where and when: Colombia, Peru, and Ecuador from 1969 to 1979.
Known as "The Monster of the Andes," he preyed on young girls. He was imprisoned before being release on bond, after which he fled and his whereabouts remain unknown.
Where and when: Minas Gerais from 1967 to 2003.
At 14, he killed a politician. He went on to focus on inmates, but he also killed his father, eating part of his heart.
Victims: 33 confirmed, possibly 34 or more.
Where and when: Chicago area from 1972 to 1978.
Known as the "Killer Clown," Gacy lured boys to his home where he normally suffocated them.
Victims: 35 confirmed, possibly 36 or more.
Where and when: USA from 1974 to 1978.
Regarded as charismatic and handsome, he approached women and girls feigning injury or impersonating authority, and abducted them.
Victims: 24 confirmed, possibly 27 or more.
Where and when: Hanover from 1918 to 1924.
Known as the "Vampire of Hanover," he was notorious for biting through his victims' throat before dumping them in the Leine River.
Victims: 36 confirmed, possibly between 43 and 55.
Where and when: Polotsk and surrounding rural areas from 1971 to 1985.
He strangled women and often robbed them of money and other valuables, which he would then give to his wife.
Click through the gallery to find out who the world's most prolific killers are.
Serial killers: these are the men who claimed the most lives
A ranking of serial killers by the number of people they killed
LIFESTYLE Serial killers
Crime fills the news day in and day out. But every now and then, a particularly brutal criminal surfaces, making us question everything and everyone around us. A serial killer is defined as an individual who has killed more than three victims on two or more separate occasions. Who are the worst serial killers to have walked the face of the planet in modern history?
Click through the gallery to find out who the world's most prolific killers are.