Influenza viruses are classified into several types.

Under normal circumstances, influenza viruses are mainly divided into four types: influenza A virus, influenza B virus, influenza C virus, and influenza D virus. A detailed analysis is as follows:

1. Influenza A Virus: The influenza A virus is a common type of flu and is prone to mutation. It can infect both humans and various animals and has a broad host range. Influenza A virus has multiple subtypes, among which H1N1, H2N2, and H3N2 subtypes have significant impacts on human health.

2. Influenza B Virus: The influenza B virus mainly infects humans and does not spread across species. Its mutation rate is relatively slower compared to influenza A virus, and its antigenicity is relatively stable. Influenza B virus can cause seasonal epidemics but generally does not lead to widespread outbreaks as influenza A virus does.

3. Influenza C Virus: The influenza C virus mainly infects humans and rarely causes large seasonal flu epidemics. It typically causes only mild respiratory infections, with symptoms often not obvious, and most commonly occurs in children. It poses a relatively low threat to human health.

4. Influenza D Virus: The influenza D virus is even rarer and mainly infects a few animals such as pigs and cattle, though it occasionally infects humans. The influenza D virus has a relatively stable genome and mutates slowly. Its transmission capability and ability to attack the human immune system are relatively limited.

When flu-like symptoms occur, timely rest and increased water intake are recommended, along with close monitoring of symptom changes. If symptoms are severe, prompt medical attention should be sought. Under a doctor's guidance, medications such as Lianhua Qingwen Capsules, Ganmaoling Granules, and Oseltamivir Phosphate Capsules may be used to alleviate the illness.