Abstract
Influenza is a disease contracted by millions of people every year. This paper looks into the causes, symptoms, and prevention of influenza. Influenza has different strains and different serotypes. Different hormones affect the way that influenza attacks the body, and the hormones and chemicals are researched and explained in this paper. Vaccines are highly recommended, and the different types of vaccines for the different strains of influenza are explained in this paper.
Influenza
Commonly known as the flu, influenza is an infectious disease caused by an influenza virus. The flu is a very common virus, with more than 3 million cases in the United States alone per year. The flu is easily spread, usually self-treatable, and usually self diagnosable. The flu is a short term illness and usually subsides within days to weeks. Young children, elderly adults, people with chronic disease or weak immune systems, and pregnant women are at the highest risk for contracting the disease. These groups of people are also at the highest risk of the disease making them terminally ill.
History of Influenza
Typically, influenza spreads in yearly outbreaks around the world, usually around the winter and spring. Around 250,000 to 500,000 deaths occur during the outbreaks. Death usually occurs in more immunocompromised people like the elderly, pregnant women, and young children. Pandemics are larger outbreaks that are less frequent. A pandemic is constituted as a prevalent disease that spreads across a whole country, or the world. In the twentieth century, there were three pandemics of influenza. In 1918, the Spanish Influenza pandemic had a reported ~50 million fatalities. The 1956 Asian Influenza pandemic killed two million people, and the Hong Kong influenza pandemic in 1968 had one million fatalities. The twenty-first century has seen one influenza pandemic, the H1N1 outbreak declared to be a pandemic in June 2009.
Influenza in Animals
Influenza may also affect other animals, including horses, birds, and pigs. Influenza A viruses have the potential to infect a number of animals. Ducks, pigs, whales, horses, and chickens are among the animals that can be infected with influenza A. The bird flu (Avian influenza A) has been transmitted from animals to humans. Humans can contract the bird flu by direct contact to birds with avian influenza A (or environments where the virus can be attached to a host and picked up) or through an intermediate host, like a pig.
Types of Influenza
Influenza A
There are three types of the influenza virus that affect humans: Type A, Type B, and Type C. A fourth family of influenza viruses has been proposed, influenza D. Bovine influenza was isolated in 2012. The influenzavirus A virus has one species, influenza A virus. This is the virus that is prevalent among birds and avian species. The natural hosts for a large variety of influenza A are wild aquatic birds. When these viruses are transmitted to other species they may cause devastating outbreaks in domestic poultry and humans. Type A influenza is bitterly hostile and causes the most severe disease in humans. A serotype is a group of intimately related microorganisms distinguished by a common set of antigens (Merriam-Webster 2018). Some of the different serotypes of influenza A are H1N1 (which caused the swine flu outbreak, and the spanish flu outbreak), H2N2, H3N2, H5N1, and H7N7, among others.
Influenza B
Influenza B essentially solely infects humans. Influenza B is far less common than influenza A. The seal and ferret are the only other animals that are known to be susceptible to the influenza B virus. Influenza B mutates substantially slower than type A, almost 2-3 times slower. There is only one influenza B serotype. Due to the lack of antigenic diversity, or the mechanism by which influenza alters its surface proteins to evade a host immune response, a certain degree of immunity is developed at a young age against influenza B. However, influenza B mutates enough that a prolonged immunity is not attainable. Pandemics of influenza B do not occur because of the reduced rate of the change of properties and its limited range of hosts.
Influenza C
The influenzavirus C has one species, influenza C virus. Influenza C virus infects dogs, humans, and pigs. This strain of the influenzavirus sometimes causes severe illness and local epidemcs, however, it is usually only mild and is less common than the other strains.
Mechanisms and Pathophysiology
A negative-sense single-stranded RNA virus is a virus that uses negative sense, single stranded RNA as its genetic material. This is the type of RNA virus that influenza is. The virus must first produce positive sense mRNA in order to produce necessary enzymes to replicate. Replication takes place once these enzymes are translated.
The Adrenocorticotropic Hormone
The adrenocorticotropic hormone (ACTH) is inhibited during the influenza infection and causes lowered cortisol levels. This mechanism, along with many others, have been profusely researched. When researchers know which genes are carried by the particular strands, they can predict how it will behave and infect humans. It can also predict how severe the infection will be. Viral hemagglutinin proteins will determine which species of a strain can infect and where in the respiratory tract the strain will attach to. The lethal H5N1 strain binds to receptors deep in the lungs, which makes it deadly. The difference in site of infection causes the infection to behave differently, in H5N1’s case, be rooted in the lungs and cause severe pneumonia. Proinflammatory chemokines and cytokines cause the common symptoms of the flu (fever, headache, fatigue).
Causes
The influenza virus is typically spread through airborne respiratory droplets in the atmosphere that are released when a sick person sneezes, coughs, or blows their nose. When an infected human coughs or sneezes, more than 500,000 virus particles can be spread. In rare cases, these droplets can transmit diseases from a host when talking within 6 feet. The droplets can also contaminate surfaces such as a counter top, toy, or door handle. The influenza virus can live on solid surfaces for up to two days. The length of the life of the virus once leaving the host depends on humidity and UV exposure. The lack of humidity and sunlight in the winter aids the flu’s survival on surfaces during flu season, causing it to be spread more often and easily. If you touch a surface contaminated by the influenza virus and then proceed to touch your mouth, eyes, or nose, you can acquire the disease.
Coming in contact with influenza virus particles doesn’t necessarily mean a 100% chance of getting sick. It depends on if the host started flu treatments in time, how many viral particles are contained in the droplets, and how far into the illness the host is. Humans can pass the flu on to others before they even realize they are sick. Influenza in humans is usually contagious one day before symptoms start and up to 7 days after becoming ill. Influenza can also be spread by direct transmission of saliva or mucus into the eyes, nose, and mouth of another person, and also from personal contact such as a handshake.
Symptoms
Influenza is distinguished by the sudden start of cough, fever, muscle pain, chills, runny nose, malaise, and sore throat. Thirty-three percent of people with influenza are asymptomatic. The first symptoms are usually the chills and fever. The cough of the flu can last two or more weeks. People usually recover from the flu within a week without medical attention, but the flu can cause severe illness or death in at risk people, as mentioned before. During their time with influenza, the infected person usually has aches and pains throughout their whole bodies, which are worse in their legs and back.
Treatment
Treatment of influenza includes antiviral drugs, however the antiviral drugs must be given early on in the disease and will be ineffective if given after the time mark (usually 72 hours). A rapid test for the virus can be given in a clinic to tell if you have the flu. Aside from the antiviral drugs, basic steps can be taken to make the flu more bearable. Rest, hydration, and over the counter pain medication can help reduce symptoms of influenza.
Secondary Illness
Influenza can occasionally cause secondary illness, which is what tends to cause fatalities in influenza outbreaks. Secondary illnesses from the flu include primary viral pneumonia and secondary bacterial pneumonia. Trouble breathing is a sign of pneumonia. If the infected person becomes seemingly better and then relapses with a fever, it is a sign of a secondary infection such as pneumonia.
Prevention
There are a number of ways that the influenza virus can be prevented. The CDC recommends getting vaccinated every year, and has the opinion that vaccination is the single best way to prevent the seasonal flu. Influenza can lead to hospitalization an even death and the general public should take every measure possible to prevent themselves from contracting the flu.
Vaccination
Influenza vaccines administer a small dose of influenza, and cause antibodies to develop in the body around two weeks after vaccination. The antibodies that are formed provide protection and immunity against the infection. There are different kinds of flu vaccines. The traditional trivialent vaccines are meant to protect against H1N1 (influenza A), H3N2 (influenza A), and a few other strains including an influenza B virus. Quadrivalent vaccines protect against four flu viruses. The quadrivalent vaccines protect against the same viruses as the trivalent vaccine, and also another influenza B virus.
The Center for Disease Control recommends that everyone older than 6 months of age should get vaccinated for the flu every flu season. Flu vaccination is especially important for high risk individuals. It’s best to get the flu vaccine before the flu begins spreading around your community and environment. You can get your flu vaccination in a number of locations, such as clinics, doctor’s offices, health departments, and college health centers. Some employers and schools offer them to their employees or students. Even if you don’t have a regular doctor, you can still acquire a flu shot from a local clinic or pharmacy.
You must get your flu shot every year because the body’s immune response from vaccination will decline with time. Getting the vaccine annually ensures optimal protection. Flu viruses are also always changing, and the formula for the flu vaccine is reviewed every year to make certain it is updated with antibodies to protect against the current strains of influenza circulating.
Infection Control
Other means of prevention include: avoiding close contact, staying home when you are sick, covering your mouth and nose when coughing or sneezing, hand washing, avoiding touching your eyes, nose and mouth, and keeping your body generally healthy for immunity. Avoiding close contact can help prevent the spread of the flu by obvious reasons. When a person is sick with the flu, avoiding other people so he or she does not spread the virus to others is encouraged. Staying home when sick is extremely important in preventing the flu; often people continue going to work and school while they are sick, and it spreads the flu exponentially compared to if they were to just stay at home. Covering the nose and mouth while sneezing is important while sick with influenza. Influenza is spread by droplets, and the droplets are projected by coughing and sneezing. When a person touches a surface that is contaminated with influenza and then proceeds to touch his or her eyes, nose, or mouth, they will transmit the virus into his or her body and may become sick if they do not have the antibodies and immunity to fight against it. Keeping generally healthy and fit is also important in preventing illness. Getting enough sleep, vitamins, and exercise helps the immune system build.
Discussion
Influenza is an ever changing disease. Different strains are found every year and the vaccines are reproduced every year to combat them. This could cause inconsistency in research and cause research to not be up to date.
Conclusion
Influenza infects a plethora of people every year during flu season. There are three different strains of the influenzavirus; influenza A, influenza B, and influenza C. Influenza can affect a number of species, however on certain strains can be crossed from one species to another. Crossing of influenza causes different types of influenza, like the bovine and avian flu in humans. Symptoms of the flu include a rapidly progressing fever, chills, dry cough, and muscle pain amongst others. There is no solid cure for the flu, however antivirals can be given within 72 hours of the onset of symptoms. The best way to cope with the pain from muscle aches and to control fever is by taking over the counter pain medications such as ibuprofen or tylenol. The different mechanisms of the strains of flu will determine how they present in the body. For example, the adrenocorticotropic hormone (ACTH) is inhibited during the influenza infection and causes lowered cortisol levels, and viral hemagglutinin proteins will determine which species of a strain can infect and where in the respiratory tract the strain will attach to. When the influenza becomes embedded deep in the lungs by these proteins and hormones, it can cause secondary illness. Secondary illnesses such as pneumonia is usually the cause of fatality when someone has a lethal case of the flu. The flu can be prevented in a few ways, the main method of prevention being vaccination. Vaccination is the most important factor in flu prevention. Other important factors include infection control such as frequent hand washing, staying home when you have influenza, and avoiding individuals with influenza. Keeping your body healthy in general and building your immune system is also important during flu season. This includes eating healthy, vitamin-rich foods, exercising, and sleeping adequately.