What is Type A influenza?

Sep 22, 2022 Source: Cainiu Health

Dr. Guo Xiheng

Introduction

Influenza A refers to type A influenza. Influenza A is one form of the flu, an acute respiratory infectious disease caused by infection with the type A influenza virus. Humans are generally susceptible to the influenza virus, and there is no cross-immunity among different influenza viruses, allowing for repeated infections. Influenza A is characterized by rapid transmission, strong pathogenicity, and a high fatality rate.

Influenza A refers to Type A influenza. Influenza A is one type of influenza, an acute respiratory infectious disease caused by infection with the Influenza A virus. Humans are generally susceptible to the influenza virus, and there is no cross-immunity among different influenza viruses, meaning reinfection can occur repeatedly. Influenza A is characterized by rapid transmission, strong pathogenicity, and a high fatality rate, making it highly likely to cause widespread outbreaks of Influenza A.

1. Human Factors

Infected individuals may exhibit symptoms such as sneezing or coughing, releasing over 500,000 virus particles with each sneeze or cough. After healthy adults become infected, viral load increases sharply within one to one-and-a-half days, peaks after two days, and remains high for about five days—though it may last up to nine days. Humans are generally susceptible to the influenza virus, and due to the lack of cross-immunity among influenza strains, repeated infections are possible.

2. Transmission via Objects

The influenza virus can survive briefly outside the human body, thus potentially spreading through contact with items such as paper currency, door handles, light switches, or other surfaces. The survival time of the virus outside the body varies depending on the surface: on hard, non-porous surfaces like plastic or metal, the virus can survive approximately 1–2 days; on dry tissue paper, only about 15 minutes; and on skin, just 5 minutes. However, if the virus is encased in mucus, its survival time is significantly extended—for example, it can remain viable for up to 17 days in mucus on banknotes. Therefore, susceptible individuals may easily contract the Influenza A virus and develop viral influenza by touching objects handled by infected persons.

Influenza A virus primarily spreads through respiratory droplets, and indirectly through contact with everyday items contaminated by the virus. It is advisable to avoid crowded places as much as possible and to frequently ventilate homes by opening windows.

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What does a positive antibody test for influenza A mean?

A positive antibody test for influenza A indicates infection with the influenza A virus, a common type of flu virus that is most prone to mutation. Symptoms after infection mainly include high fever, cough, runny nose, and muscle pain, with most cases accompanied by severe pneumonia. In severe cases, multiple organ failure—such as of the heart and kidneys—may occur, leading to death.

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What does type A influenza mean?

Influenza A is typically caused by an influenza A virus, which is a single-stranded RNA virus. The incubation period for influenza A is generally 2 to 3 days. After this period, symptoms such as fever, dizziness, headache, and body aches commonly appear. Fever may reach temperatures of 39–40°C, and is often accompanied by sore throat, runny nose, tearing, coughing, and other respiratory symptoms.

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How many days does a fever generally last with Type A influenza?

Fever refers to an elevated body temperature. In general, fever caused by influenza A lasts for 2 to 5 days, although the exact duration varies from person to person. Some individuals may experience a shorter fever duration, possibly around 2 days, which may be related to milder illness and an immune system that effectively combats the viral infection. These individuals may possess stronger immunity, enabling their bodies to quickly recognize and eliminate the influenza A virus.