JOHANNESBURG, 15 July 2008 (IRIN) - Rift Valley Fever (RVF) has claimed the lives of at least 20 people and killed thousands of animals since the beginning of 2008, and UN agencies warn that worse is to come unless immediate action is taken.

"A large part of population is potentially at risk ... the disease is still not under control," Marco Falcone, emergency coordinator of the UN Food and Agricultural Organisation (FAO), told IRIN.

By the end of June, Madagascar's Ministry of Health (MoH) had reported 520 suspected cases of RVF in humans in more than 20 of Madagascar's 119 districts, primarily in the north, south and central highlands.

Falcone said the official figures were "probably largely underestimated"; MoH investigators had found case numbers in rural areas largely underreported, and the real incidence of human infection should be considered much higher.

"There is a lack of knowledge of the disease and difficulty of communication, which make it hard to collect information from all the regions ... that's why many cases are not reported or identified as RVF," he added.

The latest situation report by the UN Office for the Coordination of Humanitarian Affairs noted: "During recent investigations, experts did not exclude a possibility of hundreds of cases."

RVF, a viral disease, can cause severe illness and death in both animals and humans, and is usually well established in animal populations by the time the first human cases are reported.

The vast majority of infections in humans result from direct or indirect contact with the blood or organs of infected animals. The disease also results in significant economic losses due to death and abortion among RVF-infected livestock.

To date, no human-to-human transmission of RVF has been documented, according to the World Health Organisation (WHO), but 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.

"It is the dry season in Madagascar; for now, it is quiet," Falcone said, but "we are expecting a new outbreak during the next raining season, from November through March, across the island," he warned.

Livelihoods at stake

Besides human health, food security and livestock-related industries were also at risk, and RVF was expected to have serious negative long-term economic impact. Madagascar is ranked at 143 out of 177 countries in the 2007 Human Development Index of the UN Development Programme, so another outbreak of the disease would be a setback the Indian Ocean island could ill afford.

"In a poor country, this can have disastrous consequences - rural households are already being affected by increasing food prices, mainly rice. The risk of a large outbreak ... will worsen the condition of the poorest population of the country," Falcone said.

Outbreaks "are responsible for important economic losses to farmers due to death and abortion of RVF-infected livestock. RVF has a direct impact on public health and livestock, and an indirect impact on food production, food safety, the rural microeconomy and the poorest people's welfare," according to a joint FAO and WHO report on the outbreak.

A call for immediate intervention

Experts from FAO, WHO, the World Organisation for Animal Health and the US Centres for Disease Control have assisted Malagasy authorities in the development of an Emergency Response Plan, but inadequate funding could hamper implementation.

The plan provides for disease management of affected livestock and human populations, reinforcement of livestock disease surveillance and the improvement of reporting systems and laboratory diagnostics. Raising awareness and training government staff and the population at large are also included.

The UN Central Emergency Response Fund has already released US$376,000 to FAO and WHO in support of the plan, which will cover the most urgent emergency activities for three months in six priority regions, but additional funding will be required to cover the remaining high-risk zones and ensure that interventions can run for a sustained period of time.

Falcone said FAO and WHO had appealed to donors for an additional $700,000, and warned that if the emergency plan, effective information systems and a proper evaluation and risk assessment a were not immediately put in place, "the consequences for livestock and humans could be devastating."