• SEXUAL BEHAVIOUR
• SEXUAL HEALTH
• HIV

“Sumer is icumen in”–as the 13th century English “Cuckoo” part-song puts it – at least for those of us in the northern hemisphere. As the days lengthen and the sun warms us, the cuckoo lays her eggs in the nests of other birds – she is the origin of the word “cuckold”, a man who is unaware of his wife's infidelities. This month we publish a fascinating range of research exploring influences on sexual behaviour exploration. In a paper aptly titled “Summer Heat”, Cornelisse and colleagues explore seasonal effects on sexual partner numbers and STI diagnoses, reporting that summer is indeed a time of higher partner numbers and STI diagnoses.1 You can listen to a discussion of the paper by Katy Turner and Vincent Cornelisse on our podcast page at sti.bmj.com. A complex dynamic between STI risk and reproductive history is reported by Decker et al2 in an interesting paper which explores young women's sexual behaviour with biological fathers of their child, by contrast with other partnerships. They identify higher risk for unprotected intercourse with biological fathers, a finding which may have relevance for sexual health providers. The influence of peers on behaviour is well-established in health psychology and also appears to operate within heterosexual couples. Sanchez et al3 report a higher incidence of concurrency among individuals who perceived their partners to have been non-monogamous. Schick present an interestingly detailed account of sexual acts between bisexual women and their male partners,4 which reminds us of the complexities involved in assessing condom use and sexual risk. Finally, two surveys from China explore the relationship between fees and sexual behaviour among female sex workers5 and the spatial distribution of sexual risk behaviour.6

Highly recommended this month is the editorial by Jespers and colleagues7 which highlights the global issue of adolescent sexual health while exploring the challenges and priorities identified in Kerubo et al's study of reproductive tract infections in Kenyan girls.8 The challenges to adolescents in disclosing sexual behaviour and accessing appropriate services are both profound and require urgent and culturally responsive solutions.

Another major policy issue, currently creating much anxiety and controversy in the UK, is the future of pre-exposure prophylaxis for HIV (PREP) in the UK. In an online survey of men across Scotland, Wales, Northern Ireland and the Republic of Ireland, Frankis et al9 report relatively low levels of awareness, but high acceptability. On a related note, a letter by Hennigan et al report evaluation in a single centre of a single question to identify MSM at highest risk – this deserves further exploration.10

Beyond the main themes of this month's issue there are plenty more interesting papers to look out for – a report of false negative HSV glycoprotein antigen tests;11 prevalence of Trichomonas vaginalis in unstably housed women;12 the impact of azithromycin as mass treatment for trachoma on genital chlamydia;13 a genotypic analysis of rectal chlamydia14 and the varying performance of respondent driven sampling by wave.12 For our clinical readers, we also highly recommend this month's Clinical Roundup by Lewis Haddow and Sophie Herbert–this month's focus is on the internet, and on drug use in young adults,15 and a 5 year review of the online learning resource for specialists and trainees, eHIV-STI by John Evans-Jones.16