Clinical Profile and Factors Associated with Mortality in Louse-Borne Relapsing Fever: A Cross-Sectional Study from a Referral Hospital in Addis Ababa, Ethiopia

In the crowded, high-altitude streets of Addis Ababa, a hidden danger thrives in the spaces between people. This danger is a fever caused by a tiny, spiral-shaped bacterium called Borrelia recurrentis. Unlike many other diseases that jump from animals to humans, this specific germ travels almost exclusively on the human body louse, a small insect that lives in the hair and clothing of people who cannot wash or change their clothes regularly. When a person scratches an itchy bite, they often crush the louse, and the bacteria inside the insect's body enter the skin through the scratch. Once inside, the bacteria multiply and cause a sudden, high fever that comes and goes in waves, a pattern known as relapsing fever. For centuries, this illness has been a marker of extreme hardship, striking hardest during times of war, famine, and when large groups of people are forced to live in unsanitary, crowded conditions. While modern antibiotics can cure the infection, the disease remains a serious threat in Ethiopia, the only country where it is still a constant, endemic problem. Understanding exactly who gets sick, how the illness progresses, and what signs predict a fatal outcome is crucial for saving lives in a city where poverty and displacement are common.

Researchers at Zewditu Memorial Hospital in Addis Ababa recently looked back at five years of patient records to understand the current state of this disease. They examined the files of 360 adults who were admitted with a confirmed diagnosis of louse-borne relapsing fever between 2019 and 2024. The hospital serves a large population of homeless individuals and others living in precarious conditions, making it a critical place to study this illness. The team found that the number of patients arriving at the hospital had grown significantly over the years, with a sharp spike in cases starting in late 2021 and reaching a peak in the first three months of 2024. This surge coincided with periods of civil unrest and economic instability in the region, suggesting that social turmoil drives the spread of the disease. The patients were overwhelmingly young men, with a median age of 21, and nearly 27 percent of those whose housing status was recorded were homeless.

When these patients arrived at the hospital, they presented with a mix of symptoms, but the most common complaints were vomiting, nausea, and coughing. However, the researchers discovered that the physical signs a doctor could see and feel were far more telling about a patient's survival than the symptoms the patient described. The study identified four specific clinical findings that, when present, strongly predicted that a patient would not survive their hospital stay. These were signs of central nervous system trouble, such as confusion or a lowered level of consciousness; crackling sounds in the lungs when listening with a stethoscope; signs of septic shock, where the body's response to infection causes dangerously low blood pressure; and abdominal pain. Patients who exhibited these signs were at a much higher risk of dying than those who did not. In fact, the presence of altered mental status was the single strongest predictor, increasing the risk of death by a massive margin compared to patients without it.

The study also shed light on the severe internal damage the bacteria causes. Almost all patients had dangerously low platelet counts, which are the blood cells responsible for clotting. More than 70 percent of those tested had counts so low they were classified as severe or very severe, putting them at risk of bleeding. Liver function was also frequently impaired, with a large majority showing elevated liver enzymes. Despite these severe abnormalities, the researchers noted that bleeding and jaundice were less common in this group than in some previous reports from other regions. The hospital mortality rate for these patients was 6.1 percent, meaning that out of every 100 people admitted, roughly six died. Most of these deaths happened very quickly, with the majority occurring within two days of admission, highlighting how rapidly the condition can deteriorate once it reaches a critical stage.

Treatment for the infection typically involves antibiotics, but the process of killing the bacteria can trigger a temporary worsening of symptoms known as the Jarisch-Herxheimer reaction. This happens when the dying bacteria release toxins that cause a sudden spike in fever and chills. In this study, nearly half of all patients experienced this reaction, and it occurred slightly more often in those who received a combination of antibiotics rather than a single drug. While the reaction is uncomfortable and can be dangerous if not managed, the study found that the choice of antibiotic regimen itself did not directly cause the difference between life and death. Instead, the outcome depended almost entirely on how sick the patient was when they arrived at the hospital. The researchers also looked at whether being homeless directly caused a higher death rate. While homeless patients did have a slightly higher mortality rate than those with housing, this difference disappeared when the researchers accounted for the severity of the patients' symptoms. This suggests that homelessness increases the risk of catching the disease and delays seeking help, but once a patient is critically ill, the immediate cause of death is the severity of the infection itself, not their housing status.

The findings from this study offer a clear path forward for doctors working in resource-limited settings. By focusing on the four key warning signs—confusion, lung crackles, shock, and abdominal pain—medical staff can quickly identify the patients who need the most urgent care and intensive monitoring. The rising number of cases in Addis Ababa serves as a warning that the disease is growing alongside the city's social challenges. The researchers conclude that while better clinical care can save lives, the only way to truly stop the spread is to address the root causes: overcrowding, lack of clean water, and the absence of stable housing for the city's most vulnerable residents. Without these broader changes, the cycle of poverty and disease will likely continue to drive the number of cases higher.