The journal published the letter on the heels of ministerial talks in Ghana, where a senior UN health official on Thursday said the outbreak in West Africa, the worst in the history of Ebola, may persist for several more months.
Sierra Leone, one of the poorest countries in the world, suffers a chronic lack of doctors, diagnostic tools, a disease-monitoring network and even clothing to protect health workers, the letter said.
"Many cases meeting the case definition for suspected Ebola might be going undetected and unreported because ill people and their families are opting for self-treatment with over-the-counter drugs or traditional medicine," it said.
"At present, there is little incentive for patients to seek professional diagnosis of suspected Ebola. Laboratory testing can be expensive (especially when a panel of tests is required for differential diagnosis), is unlikely to change the course of treatment, and might stigmatise an infected patient and their family."
It added: "Even if a patient wanted to be tested for Ebola, few (if any) laboratories in the region have the capacity to safely test a biosafety level 4 pathogen."
The warning came from four doctors working at the Mercy Hospital Research Laboratory in the city of Bo. The letter is headed by an American-based specialist, Kathryn Jacobsen at George Mason University in Fairfax, Virginia.
Bo has fewer than 15 doctors for a population of more than 150,000, a situation that is common across Sierra Leone as well as in Guinea and Liberia, the other countries where the epidemic is unfolding, the letter said.
"There is an urgent need to provide reliable and constant access to personal protective equipment in health-care centres across the region," it added.
The letter observed that early attempts to impose controls against the disease, by restrictions of border crossings and of sales of bushmeat had not worked -- and indeed may have backfired.
?What is certain is that these policies (and the ways that they were communicated) raised anxiety and, in some places, fuelled rumours that led to counter-productive behaviours."
The World Health Organization (WHO) gives a toll of 467 fatalities from Ebola, a total comprising confirmed or suspected cases. Ninety-nine have occurred in Sierra Leone.
Keiji Fukuda, the UN agency's assistant director-general of health security, said at the close of the 12-nation conference in Accra on Thursday it was "impossible to give a clear answer" on how far the epidemic could spread or when it might begin to retreat.
"I certainly expect that we are going to be dealing with this outbreak minimum for a few months to several months," he told AFP. "I really hope for us to see a turnaround where we begin to see a decrease in cases in the next several weeks."