Patients, on average, presented 5 days after symptom onset, and the most common manifestations of EVD during hospitalization were fever, vomiting, diarrhea, and related volume depletion requiring the administration of intravenous fluids and electrolyte therapy. Overall mortality among patients presenting for treatment was 43%, and only the age of the patient was a significant predictor of outcome. In contrast to previous Ebola virus outbreaks in which an older age was also associated with a worse outcome, the mean age of nonsurvivors in our study was low.13,14 The association between an older age and a worse outcome among patients with viral infections is often attributed to an increased number of coexisting conditions. However, in our study, the relative absence of known coexisting conditions suggests that an older age may have an independent association with mortality. We also found that patients who presented for care with the highest viral loads were the least likely to survive, as has been shown for other strains of Ebola virus.15 After adjustment for differences in age and time to presentation, this relationship was not significant. However, our study had limited power to detect all predictors of outcome because of the small number of patients.

The case fatality rate that we observed in this cohort in the capital city of Conakry was lower than the rate reported in most studies of previous EVD outbreaks1 (although not in all studies7) and was lower than the rate in most other regions in Guinea at that point in the epidemic.7,13 Clinical care at the main isolation facility near Donka Hospital was jointly provided by the Ministry of Heath, Médecins sans Frontières, and the WHO during the study period. Adherence to new guidelines promoting increased medical interventions, particularly related to the use of oral and intravenous fluids and electrolyte replacement, appropriate antibiotics, and targeted clinical laboratory testing,9 may have contributed to the reduced case fatality rate, as compared with past outbreaks. However, assessing associations between treatments and outcomes in small observational studies is challenging. In our study, there were approximately three clinical rounds per day, with two or three doctors and two or three nurses for each round, and depending on the type of personal protective equipment that was used, rounds were limited to either 1 hour or 3 hours because of the intense heat and humidity inside some types of personal protective equipment. Although we attempted to deliver oral and intravenous fluids to correct dehydration and metabolic abnormalities, care was still suboptimal. With more clinical personnel in each treatment center, better supportive care could be delivered more consistently, and we think that mortality could be driven lower.

The predominant clinical syndrome of EVD involves substantial volume loss due to vomiting and diarrhea. This requires aggressive oral and intravenous volume repletion and close follow-up to avoid further complications and hypoperfusion-associated organ dysfunction. Point-of-care diagnostic testing provided additional insights in a small number of patients, suggesting inadequate tissue perfusion — lactic acidosis, base deficits, prerenal kidney dysfunction, and low venous oxygen saturations. However, we could not perform such testing early or frequently enough to properly define the patterns. The substantial volume loss and profound electrolyte derangement from copious diarrhea represent opportunities to intervene clinically to improve outcomes. Notably, hypoxemia was rarely seen in these patients, despite attempts at aggressive volume repletion. However, this finding may still represent inadequate volume administration, and hypoxemia caused by pulmonary vascular leak may be more common in other care settings. Consideration may also be given to the empirical use of antimalarial therapy, especially if rapid diagnostic testing is not immediately available. Patients with severe gastrointestinal symptoms were also routinely treated with a finite empirical course of antibiotics with activity against gram-negative, gram-positive, and anaerobic organisms. However, the effect of this intervention remains unknown.

As has been seen in other disease outbreaks, but never before with EVD, large urban settings present special challenges to emergency health care facilities, and nosocomial transmission among health care staff members and patients represents an important potential outbreak amplification and new lines of transmission.16,17 This finding highlights the importance of rapid support for infection control, not only in dedicated isolation facilities but also within existing treatment centers that will typically receive undifferentiated patients with fever and nonspecific symptoms. Infection-control practices to protect patients and health care workers can have unanticipated negative consequences, including fewer clinical assessments, which may be compounded by limited clinician time at the bedside because of heat exposure in personal protective equipment.18,19

Limitations of our study include reliance on estimates from a discrete but relatively small cohort of patients. However, the observed mortality in Conakry (43%) has remained relatively stable (40%) between April and October 2014.20 Despite an active public health system for tracing contacts, case finding, and referral to an acute care facility, we inevitably are unable to identify all patients with suspected and confirmed EVD, since some will choose not to present to health care facilities and some will die before seeking medical attention. This potential selection bias will underestimate the number of cases and have uncertain effects on the case fatality rate for this epidemic. The inclusion of only patients who could be transported to our health care facilities may lead to a survivorship and immortal time bias, since patients with EVD needed to have survived long enough to get to a facility in order to be described and to receive certain treatments. Furthermore, selection of patients for certain treatments is subject to bias according to indication, which can lead to an overestimation of harm for certain therapies.21 Therefore, in this observational study, we are unable to validly explore relationships between treatments received and clinical outcomes, which underscores the importance of enhanced strategies for supportive care and specific therapies in future clinical trials.

Our recording of simple clinical data was also limited by an inability to take any material, including paper, outside the treatment center, by limited electricity to power onsite electronic data capture, and by unreliable Internet access. Inside the treatment facility, with too few clinical staff members, there is often a trade-off between delivering and recording care. A further limitation is the paucity of basic data regarding blood chemistry and hematology that would better characterize metabolic abnormalities and help to direct care for future patients. Point-of-care testing inside treatment centers is challenging because of a lack of time to perform testing due to high temperatures and dehydration of health care providers. Routine deployment of basic chemistry and hematology analyzers in addition to RT-PCR assays for EBOV in international mobile laboratories would alleviate this limitation and may guide further improvements in patient care.

In conclusion, we found that among patients admitted to the hospital with confirmed EVD in Conakry, Guinea, the most common clinical syndrome was one of gastrointestinal illness, intravascular volume depletion, and related complications, which highlight the importance of enhanced levels of clinical assessment and diagnostic testing, along with fluid management.