OVERVIEW
Influenza virus (influenza virus) is an important pathogen of respiratory infections, which is globally circulating in intra- and inter-annual cycles. It can cause acute respiratory diseases such as influenza, and is characterized by variable antigenicity and seasonal epidemics. It has a profound impact on humans and animals, and is recognized as a unique and important pathogen.
Epidemiology
Influenza viruses can circulate globally and cause outbreaks of varying degrees of severity. Influenza virus epidemics are distinctly seasonal from year to year, occurring mostly in winter and spring. The main source of infection for influenza viruses is infected persons, whereas the main source of infection for avian influenza is sick birds and their excreta. The main modes of transmission are droplet and direct contact. People are generally susceptible to influenza viruses, and infants, young children, the elderly and immunocompromised people are more infectious.
Diseases caused by influenza
Influenza virus infection can cause a series of respiratory illnesses, including upper respiratory tract infection, pharyngitis, tracheobronchitis and pneumonia. The onset of illness is usually rapid and the symptoms are varied. Systemic symptoms include chills, high fever, headache, dizziness, body aches and fatigue, etc. Respiratory symptoms include sore throat, runny nose, nasal congestion and coughing, etc. Some people may have gastrointestinal symptoms, such as lack of appetite, abdominal pain, abdominal distension, vomiting and diarrhea. The upper respiratory tract infection caused by influenza virus is called influenza, and the most notable symptom that distinguishes it from the common cold is high fever, which is usually 38-40°C and lasts for 2-3 days. Symptoms of influenza virus infection are non-specific and usually self-limiting, with symptoms subsiding after 3 to 5 days in adults, and the prognosis is generally good. However, a small number of infants, pregnant women, the elderly and immunocompromised patients may develop severe bronchitis or pneumonia, sometimes combined with otitis media and bacterial pneumonia.
Tests
Tests mainly include virus isolation and culture, antigen test, nucleic acid test and serologic test.
Diagnosis
Influenza viruses are not clinically specific and need to be differentiated from other viral and bacterial respiratory viruses, such as respiratory syncytial virus, coronavirus, parainfluenza virus, rhinovirus, and so on.
The diagnosis of influenza virus is mainly based on clinical symptoms and laboratory tests such as direct immunofluorescence, enzyme-linked immunosorbent assay (ELISA), viral culture, and serologic tests. Viral culture and enzyme-linked immunosorbent assay have high sensitivity and specificity in diagnosis.
Questions you may be concerned about
How can I tell if I have influenza virus infection from my blood test?
Blood tests can only indicate the presence of a possible viral infection, but cannot determine whether it is an influenza virus infection.
The number of leukocytes and their classification in the routine blood count can be helpful in determining viral infections. Generally, the ratio of neutrophils is 50~70% and the ratio of lymphocytes is 20~40%, and in viral infections, lymphocytes tend to be elevated, which may be accompanied by a decrease in the total number of leukocytes.
However, blood counts cannot be used to confirm the diagnosis of influenza virus infection. The diagnosis of influenza virus infection can only be established if there are symptoms of influenza and at least one of the following is present: a positive nucleic acid test for influenza virus, a positive test for influenza antigen, a positive culture culture isolation of influenza virus, and a 4-fold or greater increase in the level of influenza virus-specific IgG antibodies in both sera during the acute phase and during the recovery phase.
When influenza virus infection is suspected, it is recommended to consult a doctor for standardized diagnosis and treatment if necessary.
Treatment
Treatment is mainly supportive and symptomatic. Drugs such as amantadine and neuraminidase inhibitors can be used as prophylactic and therapeutic agents for influenza virus infection.
Questions you may be concerned about
How to treat influenza virus infection
The treatment of influenza virus infection mainly includes general treatment, symptomatic treatment and antiviral treatment.
1. General treatment: patients infected with influenza virus should take bed rest and drink more water. Some patients with serious conditions, such as high fever, shock, etc., should be given oxygen and rehydration therapy.
2. Symptomatic treatment: mainly use ibuprofen, acetaminophen, etc. for antipyretic and analgesic treatment, and use Pentoxyverine, Ambroxol Hydrochloride and other drugs for cough and phlegm treatment.
3. Antiviral treatment: commonly used antiviral drugs include amantadine, amantadine and oseltamivir.
The use of specific drugs should be under the guidance of the doctor. It is recommended that the patient should consult a doctor in time for standardized treatment.