In a grim assessment of the Ebola epidemic, researchers say the deadly virus threatens to become endemic to West Africa instead of eventually disappearing from humans.
"The current epidemiologic outlook is bleak," wrote a panel of more than 60 World Health Organization experts in a study published Tuesday by the New England Journal of Medicine.
"We must therefore face the possibility that Ebola virus disease will become endemic among the human population of West Africa, a prospect that has never previously been contemplated."
In the absence of new control measures, the authors estimated that the total case load would exceed 20,000 by Nov 2.
"The numbers of cases of and deaths from EVD are expected to continue increasing from hundreds to thousands per week in the coming months," the authors wrote.
As of Monday, the United Nations health organization reported that out of a total of 5,864 confirmed and probable cases, 2,811 deaths have resulted.
"The true numbers of cases and deaths are certainly higher," the authors wrote. "There are numerous reports of symptomatic persons evading diagnosis and treatment, of laboratory diagnoses that have not been included in national databases, and of persons with suspected Ebola virus disease who were buried without a diagnosis having been made."
When a virus is slow to mutate, as Ebola appears to be, the pathogen steadily wanes as the number of people who have developed immunity increases. With proper controls, experts say the virus would find it increasingly difficult to spread among the population until it eventually disappeared from humans and survived only in its so-called animal reservoir, which is believed to be a fruit bat.
In this case however, epidemiologists fear that the virus could continue to linger in small pockets, extending its life in humans and potentially mutating in a way that makes fighting it more difficult.
In an accompanying editorial, Dr. Jeremy Farrar, director of the Wellcome Trust, and Dr. Peter Piot, director of the London School of Hygiene and Tropical Medicine, said the epidemic has helped to degrade an already meager system of healthcare.
This "disintegration" would have broad consequences and "only worsen as the epidemic progresses," they wrote.
"West Africa will see much more suffering and many more deaths during childbirth and from malaria, tuberculosis, HIV-AIDS, enteric and respiratory illnesses, diabetes, cancer, cardiovascular disease, and mental health during and after the Ebola epidemic."
Farrar and Piot also warned that here was "a very real danger of a complete breakdown in civic society."
In the WHO paper, researchers presented their first, full statistical snapshot of the epidemic, which gained a foothold in December of last year and has fallen hardest on Guinea, Liberia and Sierra Leone.
The majority of patients stricken by Ebola are 15 to 44 years old, with men and women suffering at a nearly equal rates, according to researchers. The case fatality rate -- based on confirmed cases only -- is 70.8%, with a slightly lower chance of death -- 64.3% -- for those admitted to a hospital.
Although the epidemic has already killed more people than all previous outbreaks combined, researchers said the virus now wreaking havoc on some of the world's poorest nations is no more lethal or virulent than other strains.
Instead, its rapid spread is due to "insufficient" control efforts, and a "large intermixing" population that has transported the virus across borders and between rural and urban areas.
In order to stop the epidemic, researchers say the rate of transmission would have to be cut in half. This would be equivalent to vaccinating 50% of the population.
Several experimental vaccines are under development, and -- if they prove to be effective -- won't be available in large quantities for months.
Study authors made the following observations on the effects of the outbreak.
The average age of a person infected with Ebola is 32, and 49.9% of patients are male, researchers said. The age group that has been most affected by the virus makes up 44% of the total population.
The most common symptoms reported by patients included fever (87.1%), fatigue (76.4%), loss of appetite (64.5%), vomiting (67.6%), diarrhea (65.6%), headache (53.4%), and abdominal pain (44.3%).
Although the disease is infamously known for causing bleeding, "specific hemorrhagic symptoms were rarely reported (in less than 1% to 5.7% of patients)," authors wrote. "Unexplained bleeding" however was reported in 18% of cases.
People age 45 or older faced a significantly greater threat of death, as did those who suffered a number of the following symptoms: diarrhea, conjunctivitis, difficulty breathing or swallowing, confusion or disorientation and coma, unexplained bleeding, bleeding gums, bloody nose, bleeding at injection sites and bleeding from the vagina.
"The risk of continued epidemic expansion and the prospect of endemic EVD in West Africa call for the most forceful implementation of present control measures and the rapid development and deployment of new drugs and vaccines," the authors concluded.