How does the Influenza Virus Spread?

Influenza virus is referred to as influenza virus for short. It is divided into A (A), B (B), and C (C) types. The bovine influenza virus discovered in recent years will be classified as D (D) type. Influenza virus can cause infection and disease of many animals such as human, bird, pig, horse, bat, etc. It is the pathogen of human and animal diseases such as human flu, bird flu, swine flu, horse flu and so on.

Influenza virus

Influenza viruses are spherical, and newly isolated strains are mostly filamentous, with a diameter of 80 to 120 nanometers. The length of the filamentous influenza virus can reach 4000 nanometers.

The structure of influenza virus can be divided into three parts: envelope , matrix protein and core .

core

The core of the virus contains the genetic material that stores the virus's information and the enzymes necessary to replicate that information. The genetic material of the influenza virus is a single-stranded negative-stranded RNA, which is abbreviated as ss-RNA.

According to the amendment to the influenza virus strain nomenclature adopted by the World Health Organization in 1980, the naming of influenza strains includes six elements: type / host / isolated area / strain serial number / year of isolation (HnNn). Omit host information and omit subtype information for influenza B and C viruses. For example, A / swine / Lowa / 15/30 (H1N1) indicates that the nucleoprotein is type A. In 1930, the pig was used as the host H1N1 subtype influenza virus strain isolated at lowa. The strain number is 15, It is also the first influenza virus strain isolated from humans. ^[2]

Influenza virus mutations include antigenic mutations, temperature-sensitive mutations, host range, and sensitivity to non-specific inhibitors, but the most important are antigenic mutations.

Influenza virus can multiply in the amniotic cavity and allantoic cavity of chicken embryos. The proliferated virus is free in amniotic fluid or allantoic fluid, and can be detected by a red blood cell agglutination test. Although influenza virus can proliferate in tissue culture cells (human amniotic membrane, monkey kidney, dog kidney, chicken embryo and other cells), it does not cause obvious

Influenza virus has weak resistance and is not heat-resistant. The virus can be inactivated at 56 ° C for 30 minutes. Infectivity is quickly lost at room temperature, but it can survive for several weeks at 0 ° C to 4 ° C, and it can survive for a long time below -70 ° C or after lyophilization. The virus is resistant to dryness, sunlight, ultraviolet light, and

The source of infection is mainly patients, followed by recessive infection, and infected animals may also be a source of infection. The main route of transmission is droplets with influenza virus that enter the body through the respiratory tract. A few can also be infected by indirect contact with a shared handkerchief, towel, etc.

After the virus is introduced into the population, it is highly contagious and can spread rapidly. The speed and breadth of the virus is related to population density. Viruses entering the human body, if not cleared by cough reflexes, or are not neutralized by specific body IgA antibodies and non-specific inhibitors of mucosal secretions, can infect a few respiratory epithelial cells, causing cells to produce vacuoles and degeneration And progeny virions are quickly spread to neighboring cells, and then the virus proliferation cycle is repeated. The NA of the virus can reduce the viscosity of the mucus layer of the respiratory tract, which not only exposes the cell surface receptors, which is conducive to the adsorption of the virus, but also promotes the spread of the virus-containing liquid to the lower respiratory tract, causing damage to many respiratory cells in the short term. Influenza viruses generally cause only surface infections and do not cause viremia.

The target of influenza virus invasion is the epithelial cells of the respiratory tract mucosa. Occasionally, cases of invasion of the intestinal mucosa can cause gastrointestinal influenza.

The virus invaded the body by relying on hemagglutinin to adsorb on the surface of the host cell and enter the cytosol through swallowing; after entering the cytoplasm, the virus envelope and cell membrane were fused to release the contained ss-RNA; eight segments of ss-RNA were in the cytoplasm Internally encoded RNA polymerase, nuclear protein, matrix protein, membrane protein, hemagglutinin, neuraminidase, non-structural protein and other components; matrix protein, membrane protein, hemagglutinin, neuraminidase and other encoded proteins in the endoplasmic reticulum M protein and envelope are assembled on the Golgi body; in the nucleus, the genetic material of the virus is continuously replicated and forms the viral core with nucleoprotein, RNA polymerase, etc .; finally, the viral core is combined with the M protein and envelope on the membrane and released after budding Outside the cell, the cycle of replication is about 8 hours.

Influenza virus infection will cause host cell degeneration, necrosis and even shedding, causing mucosal congestion, edema and increased secretion, which will produce nasal congestion, runny nose, sore throat, dry cough and other symptoms of upper respiratory tract infection. When the virus spreads to the lower respiratory tract, it may Causes bronchiolitis and interstitial pneumonia.

The population is generally susceptible, and the length of the incubation period depends on the amount of invaded virus and the immune status of the body, which is generally 1 to 4 days. After the onset, the patient had symptoms such as chills, headache, fever, sore body, fatigue, nasal congestion, runny nose, sore throat, and cough. Within 1 to 2 days after the onset of symptoms, the amount of virus excreted with the secretion is large, and then it decreases rapidly. Uncomplicated patients began to recover on the 3rd to 4th day after onset; if complications occurred, the recovery period was prolonged. Influenza is characterized by high morbidity and low mortality, and deaths are usually caused by concurrent bacterial infections. Common bacteria are Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and so on. Complications are more common in infants and young children, the elderly and chronic diseases (

Viral infection also induces

How to prevent influenza

Influenza is an acute respiratory infectious disease caused by the influenza virus. There are no specific antiviral drugs. Early detection and early medication can achieve better results. How to prevent it?

1. Improve autoimmunity.

You can strengthen your body's immunity and fight viruses by exercising it. Normal work and life, study and work should be combined with work and rest, excessive fatigue, resulting in decreased resistance, easily infected with the virus and influenza. Strengthen nutrition, balanced diet, diet should be light, eat more vegetables and fruits rich in high vitamins, children should not eat cold drinks.

2. Insist on washing your face with cold water to enhance the adaptability of the nasal mucosa to the air. Keep abreast of weather changes and add clothing to protect against the cold according to the weather. At the same time, strengthen physical exercise to enhance the ability to adapt to the environment and the body's immunity. In addition, during a cold epidemic, try to go to less populated places and wash your hands often. When the body feels a little unwell, mild dry mouth, take medicine immediately when nasal congestion, drink plenty of water, pay attention to keep warm and rest, so that the condition improves in time. ^[7]

Studies have found that winter flu can double the risk of heart disease and stroke. During the first week of respiratory disease, the risk of heart disease and stroke more than tripled.

A study in the United Kingdom showed that influenza can lead to increased deaths from coronary heart disease because the inflammation it causes disrupts the smoothness of "dormant" clots in the arteries. The risk of people dying from a heart attack after catching the flu has risen by a third. Researchers have found that acute pneumonia caused by influenza infection can disrupt the stability of the atherosclerotic plate in the arteries. The atherosclerotic plate is a hard deposit of cholesterol and fibrous tissue that accumulates on the walls of blood vessels. When they divide, they release clots, impeding blood flow to the heart and causing a heart attack. The results of a study in the United States show that influenza vaccines not only enhance the immunity of vaccinators against cold viruses, but also prevent heart disease and stroke. A study by the University of Texas showed that people with heart disease get 67% less likely to have another heart attack after getting a flu shot than people without heart disease. As the body fights viruses or infections, the arterial aggregates become inflamed, which can lead to a heart attack. After being vaccinated, they can fight the flu virus and receive the power to prevent heart attacks. Experiments performed by the Los Angeles Samaria Hospital Heart Research show that heart attacks are particularly high in winter and fewer in summer, with an average reduction of 15-22%. Mortality in winter is also high. The reason may be that the weather is warm in summer and cold in winter. At this time, blood clotting factors are more active and the blood is thicker. Research done by the University of Maryland also shows that patients with a built-in defibrillator require more shocks in the winter or spring to stop the cardiac arrest. There were 40% more shocks than in summer and autumn. Researchers say influenza can trigger a fatal heart attack. The report shows that flu can worsen heart disease, and there is a significant increase in deaths from heart attacks during the flu season. In the United States alone, this number is as high as 90,000 per year.

American researchers pointed out at the American College of Cardiology's annual meeting that getting flu shots and staying warm during the winter can help reduce the risk of a heart attack.

Most people with heart disease in our country do not realize that they are at high risk of heart disease-related complications caused by the flu. Few people have been vaccinated against the flu. The flu epidemic in China usually starts in December or January and lasts for two months. In view of this, it is still the best time to get an annual effective flu vaccine.

US researchers say they have found a new anti-flu drug that can stop those resistant strains from multiplying, giving hope for flu treatment. A report published in the journal Science said that researchers have achieved effective results in experiments on mice. Researchers are currently experimenting with other animals to test its efficacy.

The new drug stops an important enzyme on the surface of the influenza virus (neuraminidase), preventing it from invading other cells. This enzyme makes a connection between the flu virus and human cells, and then infects new cells.

The new anti-flu drug developed by scientists can permanently attach to the enzyme, block its movement, and then prevent the virus from spreading to infect other cells. Scientists call this new drug DFSAs. Due to the effect of the drug, if the influenza virus wants to continue to move and reproduce, it can only self-destruct, so it cannot infect other cells. ^[10]

Japanese scholars produce H1N1 super virus approved crazy, human infection will undoubtedly die

In July 2014, in order to analyze the genetic changes of the influenza virus H1N1, Yoshikawa Kazuo, a professor at the University of Tokyo in Japan and Madison University of Wisconsin in the United States, developed a new variant. The modified H1N1 can bypass the human immune system and is considered to be Super virus. Once this life-threatening virus is leaked, humans will have no resistance and may cause a huge disaster. Kawaoka said he did develop the superflu virus. He said that the preliminary research report had been submitted to the World Health Organization Committee and received good reviews.

However, many scientists remain cautious about this. Some scientists believe that Hegang has extracted from the virus strain the parts of humans that cannot be defended to create a super virus, which is too crazy. ^[11]

U.S. scientists make deadly flu virus controversial, could cause pandemic

On June 11, 2014, U.S. scientists said they used a piece of the flu gene that was circulating in wild ducks to create a deadly virus that was extremely similar to the Spanish flu virus. Although researchers believe the results could help in the next flu pandemic, the experiment was still criticized by some as "reckless", "crazy" and "dangerous." The experiment was led by Yoshikawa Kazuo, a professor of virology at the University of Wisconsin-Madison. In 2011, he and the Dutch medical scientist Ron Fuhiye studied how the ability to spread the H5N1 avian influenza virus would be enhanced, but its experiments The method has been criticized. The related experiments were suspended for one year, and they were not restarted until 2013. ^[12]

Experiments with ferrets show that the new virus is more pathogenic than ordinary bird flu viruses, but lower than the "Spanish flu" virus and cannot be transmitted by droplets. Ferrets are often used to test for the hazards of the influenza virus because of some of their respiratory-like characteristics. As long as the 7 amino acids of some of the key proteins of the new virus are mutated, its transmission ability will be significantly improved, and ferrets can be easily transmitted through the air. Researchers believe that the new virus has the potential to cause an influenza pandemic in the population. ^[12]

Professor Robert May, former chairman of the Royal Society, still told the media that the work was "completely crazy" and that the entire incident was "extremely dangerous." Harvard professor Mark Lipsic also expressed concern: "Even in the safest laboratory, this is dangerous behavior. Scientists should not take such risks unless there is strong evidence that their work can save lives , But their paper did not provide. One view is that the H1N1 influenza virus that caused many people to die or even die was caused by a laboratory accident. ^[12]