Identify the "master of disguise" and dispel the misunderstanding of influenza

It's the flu season again, and everyone hopes to keep the flu virus out. But why is it that even though we are so vigilant and have even received the vaccine, we still can't be 100% immune to the flu?

It turns out that influenza viruses are masters of disguise in the virus world. They are highly variable, can evade the host's immune system surveillance, and spread between different hosts through adaptive evolution, thereby spreading and causing diseases in the human population, making it difficult to prevent. In addition, the public still has some misunderstandings about influenza, which invisibly affects the prevention and treatment of influenza. Let's talk about them in detail below.

Why influenza is a master of disguise

1. High variability: The influenza virus genome consists of multiple RNA fragments, which allow them to undergo rapid genetic mutation and recombination, resulting in frequent changes in viral surface antigens (such as hemagglutinin HA and neuraminidase NA). This antigenic variation allows the influenza virus to evade the host's immune recognition and clearance, thereby repeatedly and effectively breaking through the immune barrier of the population and causing influenza epidemics.

2. Escape from the immune system: The influenza virus continues to evolve through mutation mechanisms, enhancing its ability to bind to human cell receptors and increasing its pathogenicity to mammals. At the same time, the host's original antibodies become less targeted and unable to inactivate the virus. In addition, the mutated virus can antagonize interferon, reducing the antiviral effect of interferon. These escape strategies allow the influenza virus to persist and spread in the host.

3. Adaptive evolution: Influenza A virus can break through species barriers and acquire adaptive mutations that allow it to effectively infect and spread in new hosts, leading to influenza pandemics. This adaptive evolution enables influenza viruses to spread between different host species, increasing the risk of influenza pandemics.

4. Immune escape mechanism: Influenza viruses have evolved a variety of host adaptation strategies to achieve efficient replication and transmission, and their virulence and pathogenicity are mainly determined by several viral proteins. For example, the PB2 protein of influenza A virus can target and degrade mammalian JAK1, blocking the release of host interferon-induced antiviral proteins, and enabling the virus to escape the host's innate immune response.

Don't believe these flu myths anymore

People's misunderstandings about influenza mainly include the following:

1. Flu is the same as the common cold: This is a common misconception. Flu is an acute respiratory infectious disease caused by influenza viruses, which is different from the common cold. Common cold symptoms are usually mild, while flu symptoms are more severe and may include high fever, headache, muscle pain all over the body, etc., and flu may lead to serious complications.

2. Flu is not serious and does not require vaccination: In fact, flu can cause serious health problems and even death. Nearly 650,000 people die from flu each year, so vaccination is an important means of preventing flu and its complications.

3. Flu vaccines can cause influenza infection: This is a misunderstanding. Common flu vaccines contain inactivated viruses and will not cause influenza virus infection. Minor discomfort that may occur after vaccination, such as pain or mild fever, is a normal response of the immune system.

4. Flu vaccines can cause serious side effects: Flu vaccines have been shown to be safe and serious side effects are extremely rare.

5. You won't get the flu if you get the vaccine: Although the vaccine can provide protection, due to the variability of the influenza virus, vaccination cannot completely guarantee that you won't get the flu. The vaccine can reduce the risk and severity of the disease, but it cannot completely immunize you.

6. Flu is only prevalent in autumn and winter: Flu is not only prevalent in autumn and winter. Although the peak in northern China is generally from January to February each year, and the peak in southern provinces is generally from April to June, flu can occur at any time of the year.

7. Strong people will not get the flu: This is a myth. Healthy people may also be infected with the flu, especially when they are overly tired, hungry or sweating a lot, which gives the virus a chance to enter.

8. Treat the flu like the common cold: The flu and the common cold require different treatments. The flu requires antiviral medications, while antibiotics are ineffective against the flu.

9. Relying on "folk remedies" such as vinegar fumigation to prevent influenza: Vinegar fumigation and other methods are not effective in preventing influenza. Influenza viruses are not bacteria and cannot be killed by acetic acid. Blindly using vinegar fumigation may even aggravate the condition of some patients.

In summary, the influenza virus is a master of disguise. Compared with the common cold, the symptoms of influenza are more severe and spread faster. It can cause high fever, body aches, fatigue, cough, sore throat, etc., and even cause serious complications such as pneumonia, myocarditis, and meningitis. Especially for the elderly, children, and people with chronic diseases, influenza can be fatal. Therefore, it must be taken seriously. People who are suitable should be vaccinated in time, and good hygiene habits can be used to avoid the threat of influenza as much as possible.

Author: Li Nannan, member of the China Science Writers Association, expert on popular science in China

Reviewer: Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert