How to determine whether it is a relapse or influenza A

Generally, "A flu" refers to influenza A, while "re-positive" refers to the phenomenon where patients previously infected with the novel coronavirus, after symptom resolution and testing negative via nucleic acid or antigen tests, subsequently test positive again. Determining whether a case is re-positive or influenza A requires comprehensive consideration of multiple factors including medical history, symptoms, fever patterns, blood routine tests, and antibody status. Detailed analysis is as follows:

1. Medical History

Re-positive patients have a clear history of prior novel coronavirus infection and may develop symptoms again after a period of recovery. In contrast, individuals with influenza A may have had recent contact with influenza A patients or been in high-incidence areas or settings for influenza A, but may not necessarily have a history of novel coronavirus infection.

2. Symptoms

Re-positive cases may exhibit a wide range of symptoms, including not only common symptoms such as fever and cough, but also fatigue, diarrhea, and impaired sense of smell or taste. Some patients may experience mild or even no obvious symptoms. In contrast, influenza A is characterized by prominent systemic symptoms such as high fever, headache, muscle pain, and fatigue, while respiratory symptoms may be relatively mild compared to systemic symptoms.

3. Fever Pattern

The severity and duration of fever in re-positive cases can vary greatly, ranging from low-grade fever to high fever, which may persist for several days or occur intermittently. In contrast, fever caused by influenza A typically develops abruptly, with body temperature rapidly rising to 39°C–40°C and generally lasting for 3–5 days.

4. Blood Routine Features

In the early stage of re-positive cases, total white blood cell (WBC) count may be normal or decreased, with reduced lymphocyte count. In influenza A, total WBC count is usually normal or decreased, with a possible increase in lymphocyte percentage. However, in severe cases, total WBC count and neutrophil count may increase.

5. Antibody Status

In re-positive cases, specific IgG and IgM antibodies against the novel coronavirus may show dynamic changes—for example, IgG antibody titers may rise again. In contrast, specific IgM and IgG antibodies against the influenza A virus may be positive, with IgM positivity being particularly indicative of recent infection.

It is important to maintain a clean living environment, regularly ventilate rooms by opening windows, wash hands frequently with soap or hand wash and running water, and reduce the risk of virus transmission.