The Ebola crisis in West Africa may be far worse than previously thought, according to the World Health Organization (WHO), which on Thursday warned that the number of reported cases “vastly underestimates the magnitude of the outbreak.”

With some 1,069 deaths and 1,975 cases of infection reported so far, the Ebola epidemic spreading through Sierra Leone, Guinea, Liberia and Nigeria is the deadliest on record. The WHO last Friday declared the viral outbreak as an international public health emergency.

In a statement released Thursday, the WHO said it “is mapping the outbreak, in great detail, to pinpoint areas of ongoing transmission and locate treatment facilities and supplies.” It added that it is “coordinating a massive scaling up of the international response, marshalling support from individual countries, disease control agencies, agencies within the United Nations system, and others.”

Stating that “practical, on-the-ground intelligence is the backbone of a coordinated response,” the WHO on Thursday said it expected the outbreak to continue for some time. “Our operational response plan extends over the next several months,” it added.

Meanwhile, international agencies are looking into emergency food drops and truck convoys to reach people in Liberia and Sierra Leone, who have been cordoned off from the outside world in an attempt to restrict the spread of the virus.

"Trucks full of health materials and carrying health personnel are going to all the border points with Liberia and Sierra Leone," Aboubacar Sidiki Diakit, president of Guinea's Ebola commission, told Al Jazeera.

Over 370 people have died in Guinea since the outbreak began in March. 

Although there is no licensed treatment for Ebola, doctors in the affected countries are turning toward ZMapp -- an untested Ebola drug manufactured by San Diego-based Mapp Biopharmaceutical.  Two Americans and a Spaniard have so far received the drug and three doses of ZMapp have also been handed over to the Liberian government.