Influenza A and Influenza B: similarities and differences between the two brothers

This is the 4739th article of Da Yi Xiao Hu

"My child just got infected with influenza A and then got infected with influenza B", "I thought influenza A was already very fierce, but I didn't expect influenza B to be even more fierce", influenza B has become one of the focuses of public attention after influenza A, and topics related to "influenza B" have quickly topped the hot search list. What is the relationship between influenza B and influenza A? What are the similarities and differences between the two?

1. The pathogens of the two are different

Influenza is an acute respiratory infectious disease caused by influenza viruses. Influenza viruses are mainly transmitted through respiratory droplets produced by sneezing and coughing of infected people. They can also be infected through direct or indirect contact with mucous membranes such as the mouth, nose, and eyes. Influenza viruses can be divided into four types: A, B, C, and D. The main types of influenza that cause seasonal epidemics are influenza A and B viruses. The composition of influenza A and B viruses will also change alternately in different influenza seasons or different periods of the same influenza season. Influenza A and influenza B are two different subtypes of influenza viruses. They both contain two main surface proteins, hemagglutinin and neuraminidase, but their structures are different, resulting in large differences in antigenicity between them, but not much difference in pathogenicity.

Second, there are differences in infectiousness

In terms of infectiousness, influenza A is highly infectious and can easily cause widespread transmission, while influenza B is less infectious and usually only spreads within a certain area. Influenza A is highly infectious, easily mutated, and has a wide range of transmission routes, including airborne droplet transmission and direct contact transmission, which can easily cause large-scale epidemics. In contrast, influenza B (influenza B) is mainly caused by influenza B virus, which is relatively less infectious and usually only breaks out in a local area. The transmission route of influenza B virus is similar to that of influenza A, but the degree of mutation is lower.

3. Symptoms are different, but not big

There are some differences between the symptoms of influenza A and influenza B. The symptoms of influenza A (H1N1) are usually more obvious and severe, including systemic symptoms such as high fever, sore throat, cough, fatigue, headache, muscle pain, etc. The influenza A virus affects the human immune system, making people with weak bodies more susceptible to other diseases. The symptoms of influenza B (H1N1) are relatively mild, but there may also be systemic symptoms such as high fever, sore throat, cough, headache, muscle pain, etc. Compared with influenza A, influenza B has fewer complications, but it may also lead to serious diseases such as pneumonia.

In fact, people have bone pain regardless of influenza A, influenza B or COVID-19. This is because when the virus enters the body, it destroys immunity and releases inflammatory mediators, such as prostacyclin. Inflammatory mediators circulate throughout the body through the blood, and when they act on bones, they cause bone pain in patients. In general, it is difficult to distinguish what type of virus infection it is simply based on symptoms.

4. There is no cross immunity between the two

Influenza A and influenza B are two subtypes of influenza, but the antigenicity of the two viruses is different. There are certain differences between them, so having influenza A does not produce complete cross-immunity to influenza B. After being infected with influenza A or influenza B, if the patient's physical condition is relatively weak, it is still possible to be infected with another subtype of influenza virus. The influenza vaccine can prevent both influenza A and influenza B, and the probability of people who have been vaccinated contracting influenza A and influenza B successively is relatively low.

5. Treatment methods are basically the same

Both treatments require adequate rest and avoidance of exertion. Oral antipyretics, such as ibuprofen or acetaminophen, should be avoided under the age of 15. Aspirin can cause Reye's syndrome (a brain disease).

Influenza A and influenza B respond similarly to anti-influenza drugs. It is recommended to take anti-viral influenza drugs within 48 hours (preferably within 36 hours) after the onset of symptoms for the best effect. Severe vomiting, diarrhea and dehydration require timely rehydration and symptomatic treatment.

Both influenza A and influenza B are caused by viruses. The antibiotics we usually use, such as penicillin and cephalosporin, are drugs against bacteria and are useless against influenza B. Therefore, it is not recommended that you use antibiotics without authorization when you have a fever.

Author: Hematology Hospital, Chinese Academy of Medical Sciences

Wang Hailong