What are the four stages of the flu course?

Mar 06, 2025 Source: Cainiu Health

Dr. Ren Yi

Introduction

Influenza, commonly known as the flu, typically progresses through four stages: incubation period, prodromal period, fever period, and recovery period. If any abnormalities occur, it is recommended to seek medical attention promptly. If diagnosed with influenza, patients can, under a doctor's guidance, take medications such as Lianhua Qingwen capsules, Ganmaoling granules, or Oseltamivir phosphate capsules to alleviate symptoms and shorten the duration of the illness.

Influenza, commonly known as the flu, typically progresses through four stages: incubation period, prodromal period, febrile period, and recovery period. If abnormalities occur, timely medical attention is recommended. The specific stages are as follows:

1. Incubation period: This is the initial stage of influenza. During this period, the patient has already been infected with the influenza virus but has not yet developed noticeable clinical symptoms. The incubation period varies among individuals and generally lasts about 7 to 10 days. During this stage, the influenza virus starts replicating and spreading within the body and the patient is already contagious.

2. Prodromal period: This is the second stage of influenza. The patient begins to experience mild symptoms such as chills, fatigue, body aches, and nasal congestion. These symptoms may last for several hours to several days and indicate that the illness is about to progress to the next stage. During this stage, the patient may feel unwell but has not yet developed significant fever or respiratory symptoms.

3. Febrile period: This is the third stage of influenza and is the phase with the most prominent symptoms. During this stage, the patient develops a high fever, with body temperature reaching above 38.5°C, accompanied by headache, muscle pain, cough, sore throat, and other respiratory symptoms. The febrile period generally lasts about 4 days, although the exact duration may vary depending on individual differences and virus type.

4. Recovery period: This is the final stage of influenza, during which the patient's condition gradually improves, body temperature returns to normal, and respiratory symptoms gradually subside. The duration of the recovery period varies among individuals and generally takes about 3 to 7 days. During this stage, the patient should focus on rest and nutrition to promote full recovery.

If influenza is diagnosed, patients can take medications such as Lianhua Qingwen capsules, Ganmaoling granules, and oseltamivir phosphate capsules under a doctor's guidance to alleviate symptoms and shorten the duration of the illness.

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The four stages of lobar pneumonia and their pathological manifestations

The four stages of lobar pneumonia are the congestion stage, red hepatization stage, gray hepatization stage, and resolution stage. The congestion stage is characterized by alveolar congestion and edema, accompanied by chills and high fever. In the red hepatization stage, the lung lobe or segment appears dark red, with rust-colored sputum production. During the gray hepatization stage, the alveoli appear gray, accompanied by impaired breathing and dyspnea. In the resolution stage, the alveoli begin to return to normal and symptoms gradually subside.