In 1911 Francis Peyton Rous, a pathologist at Rockefeller University in New York, observed something that seemed impossible: he could transmit a malignant tumor to a bird, particularly a healthy chicken, simply by exposing it to cell-free filtrate from another diseased chicken. Or put another way: there was a type of virus, known today as retroviruses , that were capable of producing cancerous tumors. His proposal was received with great skepticism among the medical community, who did not believe that this was possible. And despite the fact that 55 years later he received the Nobel Prize for his discovery, no one then could have imagined that a retrovirus was going to be responsible for one of the five deadliest pandemics in history . Today, 36 million dead.
West Africa, year 1900. In the forests of southern Cameroon, little accessible to humans, chimpanzees lived with a virus known as SIVcpz or simian immunodeficiency virus . It is not known how long he had been among them, but it was not particularly worrying either, since the few humans who came into contact with him through his blood and the consumption of his meat – highly appreciated by the locals – were not infected. However, the ability of viruses to adapt to the environment is very high, and little time had to pass for the SIV to make its home in the human body. Of the thousands of random mutations that appear in his genetic material, there were a few that allowed him to open the key to our cells. And from there, Castilla is wide.
During the first two decades of the 20th century, HIV or human immunodeficiency virus was contained in the small communities that lived in that area. Its expansion was very slow due to the little contact that existed between the different villages. During that time it was strengthening its new way of spreading: through sexual intercourse. And sometime between 1930 and 1940 he traveled up the Congo River to a rapidly expanding urban hub: the city of Kinshasa. Named the capital of what was then called the Belgian Congo in 1929, the city was growing exponentially: people from all over the world came to it in search of new opportunities.
And for a virus that was like opening an all-you-can-eat buffet.
Settled in the capital, HIV began to spread throughout the African continent using two routes: sexual contact and the use of contaminated medical equipment . Of the two main strains of this virus, HIV-1 and HIV-2, the first is the cause of the global pandemic that followed; the second strain is confined to Africa. Within the HIV-1 strain, several groups are distinguished, the most important being M, responsible for more than 90% of infections. In turn, in this group we can distinguish several subtypes scattered throughout different regions of the planet. Thus, subtype A is common in East Africa while subtype B is dominant in Europe, America, Japan and Australia. The efforts of scientists to identify its origin have borne fruit: in July 1960, after the independence of the Congo, the United Nations sent French-speaking experts and technicians from around the world to help fill the administrative gaps left by the departure of the government. Belgian. In 1962, a large group of Haitians joined the nearly 4,500 experts already in the country.
This was the turning point in the infection, which ended up turning it into the pandemic that would devastate the planet: various studies suggest that the vast majority of infections that occur outside of sub-Saharan Africa have their origin in a single unknown person who was infected with HIV in the Congo , traveled to Haiti, and then brought the infection to the United States around 1969.
Of course, this is not to say that the virus was not already circulating in that country: apparently, the first documented case of AIDS in the United States was a Missouri teenager named Robert Lee Rayford, who died of pneumonia in 1969. This in itself is not sign of nothing unusual, but he suffered from other symptoms that perplexed the doctors. Thus, at autopsy it was discovered that he had lesions in his organs compatible with Kaposi’s sarcoma, a very rare type of cancer that mainly affects the elderly of Ashkenazi Jewish descent, but that had never been found among young African-Americans like Robert. Today we know that this type of cancer is a disease associated with AIDS.
In 1978 the prevalence of HIV-1 among homosexuals in New York and San Francisco was 5%, suggesting that several thousand people across the country were infected. And the cause had to be found. It was a race against time because without knowing who was causing the immune system of the sick to disappear from the map, there would be no way to find a cure. In 1983 a research team from the Pasteur Institute in Paris led by Luc Montagnier, Françoise Barré-Sinoussi and Jean-Claude Chermann found a retrovirus that seemed to be behind the infections. A year later, from the other side of the Atlantic, the group led by Robert Gallo confirmed this discovery. The rest is history.
The AIDS virus has not only caused a health and social revolution that is still going on. It also forced to change the so-called dogma of molecular biology , which said that genetic information always flowed in this way: DNA – RNA – protein. In the sixties, only a small and combative group of scientists thought that the virus discovered by Peyton Rous was the cause of certain tumors. The truth is that it was an unthinkable idea: an RNA virus passing its genetic information to the DNA of the cell! In 1970 two molecular biologists, Howard Martin Temin and David Baltimore independently discovered how it did it: through an enzyme called reverse transcriptase. With this it was possible to understand how the AIDS virus inserted its genetic material into human cells: the transcriptase copies the RNA of the virus and passes it to DNA, which is inserted into the human genome as if it were one more component.
Now, HIV is subtle and malicious. It is not only capable of inserting itself into the DNA of our cells, particularly those of the immune system (CD4+ T lymphocytes), where it replicates and destroys them. It also takes its time: it can wait for years , in a dormant state, and be reactivated at any time. It is because of this characteristic that this type of virus is called Lentivirus .
