A study released on Wednesday has released new information about HIV/AIDS. The Democratic Republic of Congo has recently found out that a genetic analysis of a biopsy sample from their country dates back for more than a century and contains the virus.

Michael Worobey of the University of Arizona in Tucson, who led the study, discovered that the new analysis pushes the discovery of the virus 30 years earlier, in 1900. HIV-1 is the most common form of the virus and it had been firstly found in chimpanzees. Now, the virus affects more than 33 million people all around the world.

The first HIV case in the U.S. was discovered back in 1981 and worldwide, the first case was found from a blood sample found in a man who lived in the Belgian Congo, in 1959. Geneticist Bette Korber of Los Alamos National Laboratory in New Mexico, who did an analysis in 2000, said that "the HIV virus evolves incredibly quickly. Those mutations get passed on to the next individual. So we have that evolutionary pace to enable a look backward."

The researchers have tried to track the origin of the virus by a genetic technique through which they can determine the mutation rates of various sub-types of the virus. Knowing the rate of mutations, the researchers can easily go back with their analysis and see the exact date when they had happened.

The new study was published in the journal “Nature” on Wednesday, adding lymph node tissues from a woman who had died in 1960 in the Belgian Congo. The University of Kinshasa has been keeping nearly 800 samples of tissues, which were also preserved in ice cubes.