The cases, it added, were of the "Neisseria meningitides W135" type of the disease. They were found in Riyad, Adamata and Abu Seroj IDP camps in West Darfur State.

"According to the Sudanese Federal Ministry of Health's standard operating procedures, one laboratory confirmed meningitis case raises the alert flag in any IDP camp," Sacha Bootsma, WHO communications officer in Khartoum, told IRIN on Thursday.

The cases, however, Bootsma noted, did not occur in the same week and not in the same IDP camp, and could therefore not be considered an official outbreak.

Meningitis is an infection of the meninges; the thin lining that surrounds the brain and the spinal cord and is caused by microbes that are often found in airborne dust. Several different bacteria can cause meningitis, but "Neisseria meningitides" is one of the most important because of its potential to cause epidemics.

Overcrowded housing and large population displacements due to crises, pilgrimages and regional markets facilitate the transmission of "Neisseria meningitides".

The disease, according to Bootsma, is potentially fatal and should always be viewed as a medical emergency.

"Even when the disease is diagnosed early and adequate therapy instituted, five percent to 10 percent of patients die, typically within 24-48 hours of onset of symptoms," Bootsma added.

Currently WHO recommends mass vaccination in every district that is in epidemic phase, as well as those contiguous districts in alert phase, to contain the disease.

"In response to a recent outbreak situation in Saraf Omra [IDP camp], North Darfur, where five laboratory confirmed Neisseria meningitides W135 cases were reported, a mass vaccination campaign was implemented. More than 30,000 persons were vaccinated. As a result, the weekly attack rate has declined," Bootsma said.

According to the latest WHO update on the meningitis situation in Sudan, 118 cases of suspected meningococcal meningitis had been reported in IDP camps across Darfur since January, resulting in 8 deaths. About a third of the cases occurred in Saraf Omra IDP camp.

Meningitis occurs mainly between December and June. Because of dusty winds and upper respiratory tract infections due to cold nights, the local immunity diminishes, increasing the risk of meningitis.

Bootsma estimated that the peak of the meningitis season in Darfur occurred in April and May. However, sporadic cases of meningitis occurred all year round.

Earlier this year, cases of Neisseria meningitidis had been reported in the eastern Sudanese states of Gadaref and Blue Nile, bordering Ethiopia. Between 22 January and February 2, a total of 169 cases, including 23 deaths, were reported from both states.

The first known meningitis outbreak in Sudan occurred in 1950-51, affecting 72,162 people. The second was in 1988-89 with 38,805 cases and 2,770 deaths. The most recent reported outbreak in Sudan occurred in 1999, where about 33,216 cases and 2,306 deaths were reported.