What Is Viral Replication?

RNA virus is a kind of ^[1] virus, belonging to the first class. Their genetic material is RNA ribonucleic acid. Usually its nucleic acid is single-stranded (ssRNA single-stranded RNA), but also double-stranded (dsRNA double-stranded RNA). Single-stranded RNA viruses can be divided into positive, negative and double translation RNA viruses according to their meaning Positively translated RNA viruses are similar to mRNA and can be directly translated into proteins by ribosomes; negatively translated RNA viruses require the function of RNA polymerase to synthesize positively translated RNA complementary to itself using the template as a template, and then use this RNA as a template. mRNA translation protein.

RNA virus

RNA virus is ^[1]

Viral

The process of combining newly synthesized viral nucleic acids and viral structural proteins into virus particles in infected cells is called assembly, and the process of transferring from inside cells to outside cells is release. most

In recent years, in

RNA and

Undergraduate virus morphology and

There was a murderer that killed at least 20 million people worldwide more than 80 years ago. It has never been tried in justice. It is the famous "Spanish flu virus". Scientists believe that studying the 1918 "Spanish flu", which is full of mischief, may help humans prevent another catastrophic flu attack. Today, 1918 is vague in people's memory. That year, World War I ended with the defeat and surrender of the Allies. The war killed more than 10 million people and displaced more. After four years of tragic war, people look forward to a peaceful and peaceful life. At this moment, however, a much larger disaster dwarfed the ghosts of World War I death. This disaster, which is only a small footnote in many history books, is the so-called "Spanish flu."

RNA virus 's most dangerous cold

"Spanish flu" is also known as "Spanish Lady", but it is somewhat misnomer. First, it does not seem to have originated in Spain. Second, the flu is definitely not as gentle as its name. Existing medical information indicates that "Spanish flu" first appeared in Funston military camp in Kansas, USA. Before lunch on March 11, 1918, a soldier in this barracks felt fever, sore throat, and headache and went to the army hospital to see a doctor. The doctor thought he had a common cold. However, what happened next was unexpected: by noon, more than 100 soldiers had similar symptoms. A few days later, there were already more than 500 "cold" patients in the barracks. In the ensuing months, signs of this "cold" appeared across the country. At this stage, the flu epidemic in the United States does not seem to be so serious. Compared with previous years, the mortality caused by this flu is not much higher. Before the end of a world war, few people in the military noticed the outbreak of the flu-even though it spread almost all over US military camps.

Subsequently, the flu reached Spain, causing a total of 8 million Spanish deaths. This time the flu was also called "Spanish flu". In September, the flu appeared in Boston, the beginning of one of the worst stages of the "Spanish flu." In October, domestic mortality from influenza reached a record 5%. Large-scale movements of troops during the war fueled the spread of the flu. Some people suspect that the disease is caused by the Germans' bacterial warfare or by mustard gas. This time the flu showed a rather strange characteristic. In the past, the flu was always easy to kill old people and children, but this time the death curve showed a "W" type-young adults aged 20 to 40 have also become the object of death chase. . In February of the following year, the "Spanish flu" ushered in its relatively mild third phase. A few months later, the "Spanish flu" disappeared on the planet. However, its loss to humans is incalculable. Scientists estimate that between 20 and 40 million people have been killed in the flu disaster. By comparison, the 10 million deaths caused by World War I were only 1/2 to 1/4 of it. It is estimated that the life expectancy of Americans has fallen by 10 years after the flu.

RNA Virus Disguise Killer

As an infectious disease, influenza has a history of at least 2000 years. In 1918, the harm of the "Spanish flu" even surpassed the plague outbreak in medieval Europe, and it was a tie with the AIDS epidemic in the past 20 years (about 70 million people worldwide contracted AIDS and 20 million died). Influenza is a more serious illness than you think. Even if the flu has a mortality rate of only 2.5%, if 1 billion people are infected, the consequences would be a disaster like the Spanish flu. Another danger of flu is its instability: this year you got the flu and you got some immunity. But you may still not escape that flu next year. In contrast, infectious diseases such as rubella or smallpox can gain life-long immunity just once.

The structure of the flu virus determines that it can always attack you. The genetic material of influenza viruses is single-stranded ribonucleic acid (RNA), not the genetic material DNA in your body. There are two kinds of proteins that stick to the protein shell of influenza virus like pins, one is called hemagglutinin (HA) and the other is called neuraminidase (NA). The role of HA and NA is to make the virus --- ready to invade the cell and already replicated and assembled in the cell-smoothly enter and exit the cell. The human immune system also uses HA and NA as "targets". If there is a change in the RNA of the influenza virus that directs HA and NA synthesis (this change is more likely than DNA change), then the body's immune system is "ignoring" the changed structure of HA and NA. Until the flu heals, you finally have the ability to recognize new HA and NA, but unfortunately: the next time the HA and NA of the flu virus may become unrecognizable by your immune system. 15 HA and 9 NA have been discovered to date. Scientists use HA and NA to identify the various influenza viruses. For example, the "Hong Kong type" influenza in 1968 was called H3N2.

Although most people may not know or have long forgotten the "Spanish flu" of 1918, scientists have remained vigilant. Understanding the cause of the disaster 85 years ago could help prevent a repeat of the tragedy. Finding the cause of a disease nearly a century ago is not easy. It was not until the 1930s that humans isolated the influenza virus. In the 1950s, the United States organized an expedition to rush to Alaska to dig up the body of a patient who died of the "Spanish flu" in 1918, hoping to obtain pathogens for research. Unfortunately, those burial bodies buried in permafrost have lost their research value due to thawing and decay.

It wasn't until 1997 that a research team led by Jeffery Taubenberger, a pathologist at the U.S. Military Pathology Institute, first found the RNA fragments of the cold virus that caused the "Spanish flu." Taubenberger's research institute has kept tissue samples from patients for nearly a century, including lung tissue from patients with "Spanish flu" soaked in formalin. Of the 28 samples of that year, only a 21-year-old soldier's lung sample fully matched the condition of the Spanish flu at the time. It was in this specimen that Tauben Berger used reverse transcription polymerase chain reaction to find 9 RNA "fragments" of the influenza virus of the year. RNA is easier to break down than DNA, but the fragments of RNA found by Taubenberger have already provided clues to the "Spanish flu" virus. These nine RNA fragments belong to five different genes, including genes that make HA and NA.

By comparison, Taubenberger found that the virus that caused the "Spanish flu" pandemic was similar to swine flu. If it was classified, it should be H1N1. Previous theory suggested that the pathogen that caused the 1918 influenza pandemic could be a bird flu. In 2001, Australian scientist Mark Gibbs made further discoveries based on Taubenberger. Gibbs compared the gene responsible for producing HA in the 1918 influenza virus with the same genes in 30 similar swine flu, bird flu, and human influenza viruses, and found an interesting phenomenon: in the front of this gene And the back is the code for the human influenza virus, and in the middle of the gene is the code for the swine influenza virus. Gibbs believes that the cause of the 1918 global pandemic was that a segment of the swine flu virus "jumped" into the RNA of the human influenza virus.

RNA virus continues to be tracked

However, some scientists believe Gibbs's evidence is insufficient. They believe that the HA gene of this human influenza virus and the HA gene of swine influenza virus are "mixed" (which scientists call "recombination") unlikely. Taubenberger even thought that Gibbs "misunderstood" his data.

To fully understand why the Spanish flu is so vicious, it may be necessary to determine the entire sequence of its genome. Some scientists are trying to dig up the graves of more people who died of the 1918 flu. John Oxford, a professor at Queen Mary's School of Medicine in London, is one of them. Last year, he planned to take a lung sample from the body of PhyllisBurn, a 20-year-old woman living in South London. Byrne died of "Spanish flu" that year, and she was buried in a sealed lead coffin filled with alcohol. Oxford believes that there is a well-preserved "Spanish flu" virus in Bourne's body. There is some danger in reinvestigating the Spanish flu. Scientists suggest conducting research in the best biosafety laboratory to prevent the "Spanish flu" virus-if it can be found in its entirety-from leaking out of the laboratory and endangering humans again. But in contrast, nature is the ultimate "bioterrorist." Studies have shown that wild waterfowl are the "gene bank" of cold viruses-they have all 15 HA genes and 9 NA genes. Therefore, in recent years, various types of "bird flu" with high lethality have emerged endlessly. As pigs can be infected with both the influenza virus in waterfowl and human influenza virus, it is likely to become a virus "mixer", that is, influenza viruses with new HA and NA are produced. In this way, the human immune system may face a severe test like 1918 (so many parts of China are now banned from raising livestock within a kilometer of water).

For decades, the World Health Organization (WHO) has systematically monitored the trends of human influenza viruses throughout the world, but for swine flu, there is no good surveillance system. At a WHO conference on influenza vaccines in February this year, virologist Robert Webster suggested that the WHO should develop a vaccine against all 15 HA to prevent the emergence of something like the "Spanish flu" of 1918. Scientists continue to track "Spanish flu." In the words of Tauben Berger, more than 80 years ago, the murderer, who was full of persecution, had never been tried justice. ^[2]