It is estimated that up to 500,000 people are at risk from infection and this population is scattered over a vast area. We are sure that the number of cases discovered is only the tip of the iceberg." On January 4, eight new suspected cases of Rift Valley Fever were discovered by MSF teams in the Ijara District in the North-Eastern Province of Kenya. One of the patients died, taking the death toll to at least 67 since the outbreak began on December 7.

Medecins Sans Frontieres (MSF) started battling the outbreak on December 22 when teams began work in the town of Garissa, setting up facilities to care for patients in the hospital where 23 people had been treated for their Rift Valley Fever infection. Today, MSF teams are working in Garissa, Ijara and Tano River providing information, trying to locate infected people and treating patients.

Rift Valley Fever is a rare viral disease of which very little is known. Transmitted primarily to humans through contact with infected animal matter, such as blood or other fluids, or organs, it is also spread from livestock via the aedes mosquito. Consumption of raw milk, an important element in the diet of many nomadic pastoralists of the area, is also thought to lead to infection.

The epidemic has been triggered by extensive flooding in the region. The infected mosquito eggs are often laid around river banks and can lay dormant for years until they get submerged. Once covered with water, the eggs become infected mosquitoes which spread the virus.

The last large outbreak in the same region was in 1997, also following heavy rains. During that time in Garissa District, around 27,500 were infected and 170 died.

Only about one percent of people contracting Rift Valley Fever develop the disease in a severe form. But of those who do, around half will die.

"The great majority of people infected just suffer from headaches and influenza-like symptoms reminiscent of malaria," explained MSF emergency coordinator Dr Ian Van Engelgem. "But the severe form, like other haemorrhagic diseases, attacks the liver and can cause the patient to bleed from every orifice. There is no cure, so we are only able to treat the symptoms."

One of the biggest challenges of dealing with this outbreak is logistical.

"Much of Kenya's North-Eastern Province is not accessible by road because of the floods, so the only way we can find patients is to travel by helicopter," said Dr Van Engelgem. "Just to reach the Masalani hospital in Ijara can take up to three days by road. It is estimated that up to 500,000 people are at risk from infection and this population is scattered over a vast area. We are sure that the number of cases discovered is only the tip of the iceberg."

Another difficulty is the fear for the outbreak among the population. With such a high death rate among those contracting the severe form of the disease, many people will see no benefit in making the often long journey to a health centre. To counter this, MSF teams are undertaking awareness-raising activities to increase understanding of what Rift Valley Fever is and what measures people should take themselves.

"This is an important concern because it is likely that, with the flood waters being a perfect breeding ground for mosquitoes, this outbreak will be followed to by high numbers of malaria infections. The initial symptoms may be similar to those of Rift Valley Fever. If people are too scared to come to health centres, or simply don't see the point, then there may be even more unnecessary deaths," concluded DrVan Engelgem.