A meningitis epidemic that broke out in January in Niger has killed 75 people so far, the health minister said on Thursday.

The total number of nationwide cases currently stand at 697, the minister Mano Aghali said on state television.

More than half of the deaths have occurred in the capital Niamey but the epidemic has spread to all regions of the country, with the exception of southeastern Diffa near the Nigerian border, he added.

A previous report showed that the epidemic had affected 345 people between January 1 and March 29, with 45 fatalities.

A vaccination campaign will begin next week in the most affected zones, said Aghali. Authorities have already distributed 13,500 doses of the vaccine.

Niger, one of the world's poorest countries, is frequently prone to meningitis epidemics because of its position in the "meningitis belt" that stretches from Senegal in the west to Ethiopia in the east, according to the World Health Organization (WHO).

The disease -- an inflammation of the lining around the brain and spinal cord -- can cause death within hours. It is usually bacterial or viral and occasionally is due to fungal infections, although almost any microbe can cause it.

It is highly contagious and symptoms include a sudden rise in temperature, a stiff neck, severe headache and vomiting.