Hemorrhagic Fever with Renal Syndrome: Key Symptoms and Disease Progression

Hemorrhagic Fever with Renal Syndrome (HFRS) is a naturally occurring viral disease primarily transmitted by rodents, serving as the main reservoir for the pathogen. This illness is characterized by a distinct clinical pattern involving three major symptoms—fever, hemorrhage, and kidney damage—and progresses through five well-defined stages. Understanding these phases is crucial for early diagnosis and effective management, particularly in endemic regions.

The Three Major Clinical Features of HFRS

Fever, Bleeding, and Renal Impairment

Fever is typically the first noticeable symptom, with body temperatures rising rapidly between 38°C and 40°C, and in severe cases reaching up to 41°C. Higher fever often correlates with more intense disease progression. Alongside elevated temperature, patients frequently experience the "triad of pain"—intense headache, persistent backache, and sharp eye socket pain. This is accompanied by the "triplet of redness," marked by flushing and congestion of the skin on the face, neck, and upper chest, resembling a sunburned appearance.

Bleeding manifestations may include petechiae (small red or purple spots under the skin), gum bleeding, nosebleeds, and in serious cases, gastrointestinal or internal hemorrhaging. These occur due to increased vascular permeability and platelet dysfunction caused by the virus.

Kidney damage is a hallmark of HFRS, leading to impaired renal function that can progress to acute kidney injury if not properly managed. Early signs include proteinuria and microscopic hematuria, detectable through routine urinalysis.

The Five Stages of Hemorrhagic Fever with Renal Syndrome

1. Febrile Phase

This initial phase lasts from 3 to 7 days and is defined by sudden onset high fever, chills, muscle aches, and the characteristic triad of pain and facial flushing. Patients may also report nausea, vomiting, and general malaise. Laboratory findings often reveal leukocytosis, thrombocytopenia, and elevated inflammatory markers, signaling systemic viral invasion.

2. Hypotensive Shock Phase

Occurring around day 4 to 6, this stage results from plasma leakage and reduced blood volume, leading to hypotension and potential circulatory shock. Prolonged hypotension significantly increases the risk of severe kidney damage and multi-organ complications. Prompt fluid resuscitation and close monitoring are essential to prevent fatal outcomes.

3. Oliguric Phase

During this critical period, urine output drops below 400 mL per 24 hours, indicating acute renal failure. Patients may develop fluid overload, hypertension, and metabolic imbalances such as hyperkalemia and acidosis. Dialysis might be required in severe cases to support kidney function until recovery begins.

4. Diuretic Phase

Marked by a dramatic increase in urine production—often exceeding 2,000 mL daily and sometimes reaching 4,000 to 8,000 mL—this phase signals the beginning of renal recovery. However, the rapid fluid loss poses risks for dehydration and electrolyte disturbances, especially low sodium, potassium, and chloride levels. Careful hydration and electrolyte replacement are vital during this transition.

5. Convalescent Phase

In the final stage, urinary output gradually normalizes to around 2,000 mL per day. Most symptoms subside, and laboratory values—including kidney function tests and urinalysis—return to normal. Approximately 90% of patients achieve full recovery within two months, although fatigue and weakness may persist for several weeks longer.

Early recognition of HFRS symptoms and timely medical intervention greatly improve prognosis. Public health measures focusing on rodent control, personal hygiene, and awareness in rural and forested areas are key to reducing transmission and preventing outbreaks.