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Last week, the US Defence Secretary announced a new policy that will require US military personnel to undergo annual screening for testosterone deficiency, however some health experts have expressed concerns that this program could have negative effects. Claudia Hammond speaks with Gary Wittert, professor of medicine at Adelaide University and consultant endocrinologist at the Royal Adelaide Hospital, to understand more about testosterone and what hormone replacement therapy can do to the body.

Many babies receive a vitamin K shot after birth to prevent internal bleeding, but recently more parents are declining this potentially life-saving treatment. Dr Matthew Fox, Professor of Epidemiology and Global Health at Boston University, joins Claudia to explain what is driving this trend, and the evidence behind the jab.

Professor Rebecca Katz from Georgetown University in Washington DC and Director of the Health Security Operations Center has been monitoring disease spread and public health risks during the Men's Football World Cup, and joins Claudia to share what went well and what we have learned through this monitoring process.

A microscopic parasite, cyclosporiasis, is causing a gastrointestinal outbreak in the United States – Matthew and Claudia discuss the possible sources and what is being done to combat it. And, how El Salvador eliminated trachoma – the world's leading infectious cause of blindness.

Presenter: Claudia Hammond
Producers: Jonathan Blackwell and Georgia Christie