June 11 - By the time the truck pulled away from the morgue in Bunia, the morning heat hung heavily over the road to Mongbwalu.

The body of a 44-year-old Congolese pastor lay inside a wooden coffin strapped into the back of an aging Nissan SUV with the backseats pushed flat. A group of young relatives were crammed in, too, sitting atop the casket.

The drive across Ituri province takes about three hours, longer when the dirt roads are as dry and broken as they were that February day. The four-wheel-drive bucked violently, showering dust over the potholes, rocks and gullies carved into the red earth.

By the time the truck reached Mongbwalu, the coffin was cracked, after collapsing under the weight of those sitting on it.

These are among events being examined by investigators hunting for the "patient zero", or earliest infection, of the Ebola epidemic raging in the war-torn Democratic Republic of Congo, according to four experts on the team conducting the health ministry inquiry.

The investigators said the casket's rocky journey preceded one of the earliest suspected super-spreader events: the February 4 funeral of the man inside the coffin, Pastor Paluku Makundi Denis.

Health authorities are struggling to catch up with the mushrooming epidemic of a rare Ebola strain that kills 30% to 50% of those infected and has no vaccine or cure. The outbreak has caused about 635 confirmed infections and at least 127 deaths in eastern Congo, according to the country's health ministry. The true toll could be much higher, officials warn.

A surveillance epidemiologist on the inquiry estimated the strain, Bundibugyo, had been circulating for four to six months before Congo's official outbreak confirmation on May 15. He stressed more work is needed to determine whether Pastor Makundi, who was never tested for Ebola, was infected and to identify the outbreak's origin — a key step to understanding its scale and preventing further epidemics.

Congo's health ministry and Ituri's health authority didn't respond to comment requests. WHO chief Tedros Adhanom Ghebreyesus d...