Health authorities in Nigeria are warning that the entire country is threatened by a cholera outbreak. At least 352 people have been killed by the infection in the space of three months, and more than 6,400 cases have been reported, mostly in the north. Doctors are now monitoring outbreaks in 12 of Nigeria's 36 states. The health ministry blames the spread of the disease on heavy seasonal rains and the scarcity of clean water and proper sanitation. In a statement, it said "epidemiological evidence indicates that the entire country is at risk". The outbreak has also killed more than 200 people in neighbouring Cameroon. Cholera, a water-borne disease, causes diarrhoea and severe dehydration and can lead to death if not detected and properly treated. The infection is highly contagious yet easily preventable with clean water and sanitation. The BBC's Caroline Duffield in Lagos says medical care in Nigeria is generally poor. In many places access to toilets is rare and open-air sewers can easily flood, she says. Source: BBC