In a televised address Saturday, Prime Minister Olivier Mahafaly Solonandrasana said no public meetings or demonstrations would be allowed in the capital Antananarivo, which has seen six deaths in recent days.
“At airports and bus stations, measures will be taken for passengers to avoid panic and to control the disease,” he added after an emergency meeting with the UN health agency.
Madagascar has suffered plague outbreaks almost every year since 1980, often sparked by rats fleeing forest fires.
The current outbreak was unusual as it had affected large urban areas, increasing the risk of transmission, the WHO warned.
The outbreak is a mix of bubonic plague, which spreads by infected rats via flea bites, and pneumonic plague spread person-to-person.
The highly infectious disease killed millions of people across the world in the past before being largely wiped out.
“WHO is concerned that plague could spread further because it is already present in several cities and this is the start of the epidemic season,” Charlotte Ndiaye, WHO representative in Madagascar, said in a statement Sunday.
“Our teams are on the ground in Madagascar providing technical guidance.”
The first death this year occurred on August 28 when a passenger died in a public taxi en route to a town on the east coast.
Two others who came into contact with the passenger also died.
Officials are trying to identify people who came into contact with a basketball coach from the Seychelles who died of plague in Antananarivo on Wednesday while visiting the island for a sports event.
Plague can be cured with antibiotics but can be fatal within 24 hours if it affects the lungs.
On Saturday, the health ministry said the death toll had risen to 24 from 19 on Thursday, with more than 100 infected.
The recurrent outbreaks in Madagascar have been attributed to poor hygiene and insufficient healthcare.
The government said one girl among the dead had apparently been involved in a ceremony retrieving the bodies of deceased family members, rewrapping their remains and dancing with the corpses.
WHO has released $300,000 in emergency funds, as well as extra supplies of antibiotics and protective equipment.
It appealed for $1.5 million to fund the emergency response.
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