HIV medicines 'boost prevention'

The HIV drug tenofovir Two studies in Africa add weight to previous data showing drugs used to treat HIV can reduce infection risk when taken daily.

The World Health Organization said the studies could have "enormous impact" in preventing HIV transmission.

The findings were revealed in the run-up to an AIDS conference in Rome.

"This is a major scientific breakthrough which re-confirms the essential role that antiretroviral medicine has to play in the AIDS response," said Michel Sidibé, executive director of the Joint United Nations Programme on HIV/AIDS (UNAIDS).

"These studies could help us to reach the tipping point in the HIV epidemic."

Future hopes

One trial, carried out by the University of Washington, US, followed almost 5,000 couples in Kenya and Uganda, where one person had HIV infection and the other did not.

Continue reading the main story“Start QuoteIf you're currently trying to stay HIV negative don't give up on the condoms yet”

End QuoteLisa PowerTerrence Higgins Trust The uninfected person took a daily HIV medicine (tenofovir), a combination of two HIV drugs (tenofovir and emtricitabine), or a placebo pill.

There were 62% fewer HIV infections in the group on the single drug and 73% fewer HIV infections in the group that took the combination, compared with those given a dummy pill.

The other trial, conducted by the United States Centers for Disease Control, followed 1,200 HIV-negative heterosexual men and women in Botswana. They received either a once-daily combination tablet or a placebo. The HIV medication reduced the risk of getting HIV by about 63% overall.

A previous trial found the combination of two HIV drugs reduced the risk of infection in gay and bisexual men by 44%. But a similar study in women at risk of HIV infection in Kenya, Tanzania and South Africa produced disappointing results.

New tools

The HIV charity, the Terrence Higgins Trust, described the latest findings as "genuinely exciting".

Head of Policy Lisa Power told the BBC: "Pre-exposure prophylaxis is not going to be available overnight but we are exploring whether it is one of a range of things that can drive down onward transmission of HIV."

But she stressed that the findings needed to be properly tested and trialled.

"If you're currently trying to stay HIV negative don't give up on the condoms yet."

The WHO and UNAIDS recommend that people make evidence-informed decisions on HIV prevention options.

They say no single method is fully protective against HIV and antiretroviral drugs for prevention need to be combined with other HIV prevention methods such as condoms.

"Effective new HIV prevention tools are urgently needed, and these studies could have enormous impact in preventing heterosexual transmission," said Dr Margaret Chan, the WHO's Director-General.

"WHO will be working with countries to use the new findings to protect more men and women from HIV infection."

Violent images 'boost aggression'

The longer the boys watched the videos, the less they responded to the violence within them Repeated viewing of violent scenes in films, television or video games could make teenagers behave more aggressively, US research suggests.

The National Institutes of Health study of 22 boys aged 14 to 17 found that showing dozens of violent clips appeared to blunt brain responses.

Dr Jordan Grafman said it might make aggression feel more "acceptable".

However, a UK expert said the reasons behind violence were too complex to be explained by laboratory research.

Continue reading the main storyRelated storiesCall for child screen-time limitGames 'don't lead to violence' The effect of violent imagery on young people has been debated from the early days of television, and, more recently, that debate has expanded to include video games.

Various studies have suggested that exposure appears to have an effect on the way that the brain processes emotional responses, yet it is unclear whether this can have a direct impact on behaviour.

The US study, published in the journal Social Cognitive & Affective Neuroscience, involved 60 violent scenes from videos being collated, mostly involving street brawling and fist fights.

Continue reading the main story“Start QuoteThe suggestion is that, over a period of time, people can develop a kind of tolerance to these images - but another word for that is just boredom”

End QuoteProfessor David BuckinghamDirector of the Centre for the Study of Children, Youth and Media The violence was ranked "low", "mild" or "moderate", and there were no "extreme" scenes.

The response of the boys as they watched the clips was measured in a number of ways.

They were asked to rate whether they thought each clip was more or less aggressive than the one which preceded it, and were brain scanned using functional magnetic resonance imaging, which shows in real time which areas of the brain are active.

In addition, electrodes attached to the fingers detected increasing sweat - a sign of an emotional response.

The longer the boys watched videos, particularly the mild or moderate ones, the less they responded to the violence within them.

In particular, an area of the brain known as the lateral orbitofrontal cortex, thought to be involved in emotional processing, showed less activity to each clip as time went on.

'Social problem'

Dr Grafman said: "Exposure to the most violent videos inhibits emotional reactions to similar aggressive videos over time and implies that normal adolescents will feel fewer emotions over time as they are exposed to similar videos."

He said that this could actually produce more violent reactions from the teenager.

"The implications of this include the idea that continued exposure to violent videos will make an adolescent less sensitive to violence, more accepting of violence, and more likely to commit aggressive acts since the emotional component associated with aggression is reduced and normally acts as a brake on aggressive behaviour."

However, another academic said it was almost impossible to explain violence in these terms.

Professor David Buckingham, the director of the Centre for the Study of Children, Youth and Media, said that violence was a "social problem" with many contributing factors, not simply a matter of looking at how the brain worked.

"The suggestion is that, over a period of time, people can develop a kind of tolerance to these images - but another word for that is just boredom.

"This debate has been going on since before we were all born. In the 19th Century people were panicking about the effect of 'Penny Dreadfuls'.

"If we are truly interested in violence and aggression, rather than blaming the media for everything wrong in the world, we need to look at what motivates it in real life."