The number of plague cases has more than doubled to a total of 805 in Madagascar in the past week, according to Madagascars Office of National Risk and Emergency Management .

At least 74 people have died of the curable disease so far this year. There were 320 suspected and confirmed cases as of last Tuesday.

While plague is endemic in the island country of Madagascar, which typically sees 400 or so cases in the September-to-April outbreak season, this recent outbreak has several differences.

First, the infections began earlier in the season, with the first case in August. And, crucially, more than 70 percent of infections have been pneumonic, meaning they are airborne and spread person to person via saliva droplets when an infected person coughs, making them far more infectious and easily spread than the more typical bubonic cases, which are spread by fleas on rats.

This also means those who live in dense urban areas are at greater risk, according to Nyka Alexander, commications officer for the World Health Organization, who is based in the capital, Antananarivo, the hardest-hit city.

More of the plague [is] in urban settings or in settings where people live closer together and in areas where they dont normally have plague.

If discovered early, plague is easily curable in a few days with a round of antibiotics. But if left untreated, its nearly always fatal, according to WHO press officer Christian Lindmeier.