The influenza virus is a major cause of illness and death and one of the most significant infectious diseases threatening the world today. Although most of its victims are elderly, pneumonia-influenza is one of the top-ten leading infectious conditions listed as causing years of potential life lost by the Centers for Disease Control (http://www.medicalecology.org). Perhaps one of the most devastating reports of the influenza virus is the pandemic Spanish Flu of 1918. Approximately twenty to forty percent of the population worldwide became ill and an estimated fifty million people died.
Influenza is a contagious respiratory illness caused by flu viruses and can cause mild to severe illness, and at times can lead to death. Because strains of influenza change every year, it is important to have an understanding of what influenza actually is and how it works. What makes this virus so unique is that it is constantly mutating, which makes combating it and producing a vaccine very challenging.
Because this virus is so unique, it’s metabolic effects impact the world and the types of vaccines being made must prevent another pandemic from occurring. However, understanding the influenza virus will not eradicate it from existence, rather it will give us a better understanding of how this one virus is so resilient.
The structure of the influenza virus is an enveloped virus. Which means that the virus “steals” the membrane of its host cell before it replicates. Although there are other viruses that demonstrate similar properties, the influenza virus is very efficient at using this method to overtake a healthy cell.
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Its genome consists of eight segments of negative sense single stranded RNA and encodes for ten proteins and replication then happens in the nucleus.
Once the virus has compiled its membrane structure, it has unique assortment glycoproteins, which resemble spikes that connect to sugars called hemagglutinin (HA) and neuraminidase (NA). Currently there are roughly seventeen different hemagglutinin subtypes and ten different neuraminidase subtypes. The sequences of sugars within the structure of the virus will determine which general strain it is.
There are three types of influenza viruses: A, B and C. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza type C infections cause a mild respiratory illness and are not known to cause epidemics. As much as we know about the influenza virus, there are still many unknowns. This may be due to what’s known as antigenic shift.
Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans. In the spring of 2009, an antigenic shift occurred and a new H1N1 virus with a new combination of genes surfaced and infected people and quickly spread, causing a pandemic. When these shifts happen, it can leave people with little or no protection against the new virus. Once one host is infected with multiple strains, the various strains can then swap genome segments and this commonly leads to new epidemics of the virus every few years.
However, antigenic drifts are small changes that occur in the virus and happen continually over time. It produces a new virus strain that may not be recognized by the body’s immune system and works as follows: a person infected with a particular flu virus strain develops antibody against that virus. “Once the virus has penetrated the host cell, it initiates several types of viral-specific immune responses, including circulating and mucus membrane-associated secreted antibodies, interferon, and T-cell dependent responses.
The latter can be divided into two types: T-helper cells and cytotoxic T-cells. Both antibody-based and cellular-based responses combine in neutralizing the neuraminidase and haemagglutinin portions of the virus. Interferon acts against viral RNA synthesis”. As the newer virus strain appears in the body, antibodies against the older strains no longer recognize the “newer” virus, and reinfection can occur. This is part of the reason people are more susceptible to getting the flu more than one time. But how to we protect ourselves from getting the virus and how is the virus spread?
People with flu can often spread it to others up to about 6 feet away. Many experts believe droplets from people with the flu when they cough, sneeze or talk land on the mouths or noses of people who are nearby or possibly inhaled into the lungs and spread the flu virus. Because of this, people with the flu should avoid contact with other people until they are healthy. By avoiding sick people and washing your hands, not touching your eyes, nose or mouth along with forming healthy habits to keep the immune system strong, one may be able to avoid coming in contact with the virus.
However, if someone is healthy but exposed to a person with the flu, antiviral drugs may help one from getting sick and the sooner one is treated with an antiviral drug, the more likely it will prevent the flu. Antiviral drugs are seventy to ninety percent effective at preventing the flu. However, even for the healthiest person, the best way to prevent getting the virus is vaccination.
The flu vaccine is the best protection against the flu season. By getting the vaccination, one is sixty percent less likely to get sick and is shown to offer other benefits including reducing illness, antibiotic use, time lost from work, hospitalizations, and deaths. To protect people from infection, the National Institute of Allergy and Infectious Diseases (NIAID) laboratories develop new vaccines for seasonal flu viruses and animal strains that could become pandemics.
Currently flu vaccines start with chicken eggs. They take new flu strains identified as possible pandemics and inject them into an egg to grow before being harvested. From these studies they make new influenza vaccines. As the flu vaccine production process improves, the ability to quickly respond to outbreaks and potential pandemics will greatly improve. As for now, it is important to protect ones self, by trying to stay healthy, avoiding being around sick people during the flu season and of course, getting the flu vaccine annually.
An Introduction to the Virus of Influenza. (2023, Jan 09). Retrieved from https://paperap.com/an-introduction-to-the-virus-of-influenza/
