The International Federation of Red Cross and Red Crescent Societies is deploying its first-ever plague treatment centre to Madagascar after 57 people have died of the disease.
A statement on Friday said 550 cases have been reported so far.
Red Cross officials have said the situation is particularly worrying because pneumonic plague, which is spread from person to person, has occurred for the first time in non-endemic areas and crowded cities in the island nation.
About 70% of the cases are the pneumonic form.
The statement said the plague treatment centre will include 50 beds and a medical team with the capacity to isolate patients and will “significantly bolster” the outbreak response.
Authorities in Seychelles this week said a man was diagnosed with pneumonic plague after returning from Madagascar.