An anti-cholera campaign worker sprays anti-cholera disinfectant to a pond during an anti-cholera campaign in Sanaa, Yemen, on June 4, 2018. An anti-cholera campaign has been launched to prevent the outbreak of the cholera epidemic here on Monday. The United Nations has listed Yemen as having the world's number one humanitarian crisis, with 7 million Yemenis on the brink of famine and cholera causing more than 2,000 deaths. (Xinhua/Mohammed Mohammed)