At least 140 people have died in several states in Nigeria due to an outbreak of meningitis, officials have said. The current outbreak is the worst recorded in the country since 2009, when at least 156 people died.

More than 80 of the deaths occurred in north-western Zamfara State. At least 23 people died in Sokoto State, where a state of high alert was declared by the ministry of health on 20 March.

More than 1,000 people have been infected, amid fears the death toll could increase if the epidemic reaches crowded areas such as refugee camps.

It is believed the new strain of Cerebro Spinal Meningitis (CSM) is not common in Nigeria and was imported from Niger Republic, Minister of Health Isaac Adewole told News Agency of Nigeria (NAN). Thus new vaccines are required to immunise people.

Earlier in March, Adewole said a team of epidemiologists had been deployed to address the issue, stressing that the ministry was working hard to tackle the epidemic.

The minister appealed to Nigerians to report all cases of unusual fevers to health facilities and to avoid overcrowding.

"When people are coughing let them be referred to facilities, open windows and ensure that we do not get infected easily, Adewole said earlier in March, according to local media.

"Children are more susceptible and when they have unusual fever they should also be referred to the hospital."

What is meningitis?

Meningitis is an inflammation of the layers of the brain and spinal cord. Infection is the most common cause of meningitis, with viral or bacterial pathogens transmitted via saliva.

Bacterial meningitis is deadly in about one case out of ten, and life-long sequelae occur in one in five survivors. More on meningitis here.