Among the participants in this study antiretroviral treatments were estimated to have prevented 472 potential HIV transmissions; antiretrovirals suppress the viral load of retroviruses in infected people, without treatment the viral load can grow into the millions, while with strict adherence to treatment regime the virus can be suppressed to undetectable levels.
"It is not always easy for people to get tested for HIV or find access to care; in addition, fear, stigma, homophobia and other adverse social forces continue to compromise HIV treatment", he said.
The study conducted over eight years examined around 1000 male couples across Europe, where one of the partners was HIV infected and was receiving antiretroviral drugs.
The 8-year study monitored the health and activity of nearly 1,000 gay couples across Europe. Its findings add to an earlier phase of the study that looked at HIV transmission risk for serodifferent heterosexual couples who also did not use condoms.
"Our findings provide conclusive evidence that the risk of HIV transmission through anal sex when the HIV viral load is suppressed is effectively zero", the study revealed.
The study gives a ray of hope to the gay community, reinforcing that HIV transmission could be stopped if antiretroviral therapy is used.
Alison Rodger, a professor at University College London who co-led the research, told CNN's Hala Gorani that if everyone in the world had access to the right treatment, the virus could be eliminated.
She said this "powerful message" could help end the HIV pandemic by preventing the virus' transmission in high-risk populations.
Although 15 men were infected with HIV during the course of the study, DNA testing proved that all infections occurred through sex with someone other than their partner who was not on treatment.
Myron S Cohen, from the UNC Institute for Global Health and Infectious Diseases in North Carolina, said in a commentary in the Lancet that this new discovery should push the world forward to test and treat everyone with HIV. "I realize that numerous researchers and gatherings are as yet buckling down and I'm certain that like the achievement we've seen with the measles immunization and the polio antibody, that some time or another we'll have a similar accomplishment with a HIV antibody".
In the study, the men with HIV had been taking antiretroviral therapy for an average of four years before it began, making the virus undetectable, defined as fewer than 200 copies per ml of blood.
Therefore you should do yourself a favor and limit your sexual partners to one who is trusted. "It will make a great difference when you can't transmit the virus to your partner", Dr Mugo said.
Deborah Gold, chief executive of National AIDS Trust said more should be done to get the message out to healthcare workers and the public. "We think this is vital to addressing stigma".
"Now we can say zero risk, which is just so much more empowering for people".