Getting medical attention is difficult in the best of circumstances in pastoralist areas because health services are so poor. When there is drought and children become undernourished, they are often too weak to fight off opportunistic diseases such as measles that would not normally kill a healthy child. After a period of drought, sudden rain squalls bring contamination to water holes, and children can contract cholera and diarrhoea. Sudden rains also lower temperatures and increase the risk of fever and illness. Swarms of mosquitoes breed in puddles, and malaria quickly follows.