An outbreak of Rift Valley Fever (RVF) has killed 16 people and infected at least 100 in Tanzania, spreading to more regions, Health Minister David Mwakyusa said on Tuesday.

Mwakyusa said the central region of Dodoma was the worst affected by the mosquito-borne illness, which spreads from infected livestock to humans. The disease had also claimed lives in Arusha and Manyara regions, which border on Kenya, where a RVF outbreak killed at least 154 people between December 2006 and February 2007. Up to 41 people are still receiving treatment in hospitals in Tanzania after developing RVF symptoms.

Veterinary officials in Kenya have since reported that an ongoing livestock vaccination campaign has stemmed the spread of the disease in that country. A ban imposed by the Kenyan government on the slaughter of livestock in the affected areas has been lifted, but a restriction on livestock movement from 33 districts where cases of the disease had been reported is still in force.

Mwakyusa said there was no RVF vaccine for humans and advised the public to be careful when handling meat and other livestock products and the carcasses of dead animals.

"I am not asking you to avoid eating meat, but make sure that it is inspected by relevant health authorities. Don't eat nyamafu [dead animals] or sick ones. Avoid slaughtering animals when they are sick and about to die," Mwakyusa, a former professor of medicine, told reporters on Monday when he visited Dodoma.

Tanzanian authorities imported RVF vaccines from South Africa in February and embarked on a livestock vaccination campaign in affected areas in a bid to stop the spread of the disease.

The RVF virus is spread to humans from livestock via the aedes mosquito, which breeds rapidly during floods. It can be transmitted through contact with infected animal material, such as blood or organs. Consumption of milk, a staple for many pastoral people, is also thought to lead to infection. Symptoms in humans include bleeding through the nose and mouth, and liver failure.