A young boy watches as sanitation workers fumigate the street during the anti-cholera campaign, on the outskirts of Sana'a on July 16.

The United Nations has blamed the warring sides in Yemen and their international allies, including Saudi Arabia, for fueling the cholera outbreak, driving millions of people closer to famine, and for hindering aid access.

The cholera epidemic in Yemen could spread during the annual haj pilgrimage in Saudi Arabia in September, although Saudi authorities are well prepared, the World Health Organization (WHO) said on July 14.