The disease has already killed more than 171 people in Madagascar alone, with thousands more confirmed cases across the east African country.
Malawi became the 10th neighbouring nation to be placed on high alert following the deadly outbreak of the disease which wiped out a third of the medieval population.
The epidemic accounted for more than 50 million deaths across Europe during the 15th century.
Madagascar’s health authorities have installed medical checkpoints across the parts of the capital city of Antananarivo in an attempt to curb the spread of the plague.
Pneumonic plague, or lung-based plague, is always fatal in infected individuals if left untreated.
A local news crew following one health worker in the stricken city heard doctors informing residents that the new strain of the disease “can kill in three hours”.
Earlier this week, infection and immunity expert Dr Matthew Avison told Daily Star Online that the “extremely rare” disease has been “resilient” to antibiotics.
A spokesman for the World Health Organisation admitted there were fears that this strain of plague – which is now believed to be airborne – could cause a global outbreak of the disease.
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Speaking to Daily Star Online, disease outbreak expert Professor Paul Hunter said the plague could reach every continent, starting with mainland Africa.
He said: “This current outbreak is concerning given that it is different from previous cases we have seen, and has been spreading to areas that are not used to seeing it.
“We don’t want a situation where the disease spreads so fast it gets out of control.
"We are talking about it spreading in days rather than weeks.”
It comes after top secret files revealed Japanese scientists had been cultivating the killer disease during World War 2 in an attempt to use it against US forces.