Rift Valley Fever (RVF) has infected more than 400 people in Madagascar, with at least 17 fatalities, according to the Ministry of Health (MoH).

"An outbreak has been confirmed; it will be a big challenge to contain," Nestor Ndayimirije, Inter-Country Epidemiologist at the UN World Health Organisation's (WHO) Eastern and Southern Africa office, told IRIN.

The MoH said 59 cases had been positively identified by the Pasteur Institute of Madagascar, part of a global network devoted to medical issues and epidemiological screening in developing countries.

RVF is a viral disease that primarily affects animals but can also infect humans, so even when the disease has been removed from human populations "you still have to control the animal side," Ndayimirije explained.

RVF is usually well-established in animal populations by the time the first human cases are observed - the Ministry of Agriculture first reported cases among livestock on 9 April.

According to a WHO statement, the human cases were recorded the Alaotra Mangoro, Analamanga, Itasy, Vakinakaratra and Anosy regions in the East of the Indian Ocean island.

A call for help

In an effort to contain the outbreak, Malagasy authorities have established an inter-ministerial committee to oversee the response and have requested assistance from the WHO, the UN Food and Agricultural Organisation (FAO) and the World Organisation for Animal Health (OIE).

A joint mission of WHO, FAO and OIE representatives to support Malagasy efforts was expected to be in the country by 23 April, Ndayimirije said.

Meanwhile, Malagasy authorities have implemented control measures such as case management, surveillance, social mobilisation, provision of medicines, and prevention and strengthening of hospital infection control.

The vast majority of RVF infections in humans result from direct or indirect contact with the blood or organs of infected animals. To date, no human-to-human transmission of RVF has been documented, according to the WHO.

Human infections have also resulted from the bites of infected mosquitoes and RVF has commonly been associated with unusually heavy rainfall and flooding. Madagascar is just coming out of a particularly wet rainy reason: earlier this year cyclones Fame and Ivan brought powerful winds, heavy rains and flooding that affected over 330,000 people, of whom 190,000 lost their homes.

"While some infected people experience no detectable symptoms, others develop flu-like fever, muscle pain, headaches, joint pain, vomiting, loss of appetite and sensitivity to light. In more severe cases patients can also experience lesions in their eyes, neurological problems, liver impairment and haemorrhagic fever symptoms, including widespread bleeding," the WHO statement said.

RVF was generally confined to Sub-Saharan Africa until outbreaks were reported in Saudi Arabia and subsequently in Yemen in 2000.