Influenza or flu is a common viral disease of the upper respiratory tract. Influenza is a highly infectious viral illness. It affects mainly the nose, throat, bronchi and, occasionally, lungs. Infection usually lasts for about a week, and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive cough, sore throat and rhinitis.
The name “influenza” originated in 15th century Italy, from an epidemic attributed to “influence of the stars.” There are three types of influenza virus: A, B and C. Major outbreaks of influenza are associated with influenza virus types A or B. Infection with type B influenza is usually milder than with type A. Influenza C is common but rarely causes disease. It is a seasonal illness that occurs each winter in Wisconsin and throughout the United States. It is not a reportable disease in Wisconsin, and the annual number of cases is unknown.
Influenza is spread from person to person when droplets of moisture from a person with influenza are spread through the air when that person coughs, sneezes or talks. These droplets contain viruses that when inhaled by another person can cause an infection. According to the National Institutes of Health, between 5% and 20% of Americans get the flu each year. More than 200,000 people are hospitalized and 36,000 die annually because of flu in the United States.
Influenza disease can occur among people of all ages; however, the risks for complications, hospitalizations, and deaths are higher among people age 65 years or older, young children, and people of any age who have certain medical conditions. Pregnancy also increases the risk for serious medical complications from influenza.
Causes
The influenza virus particle – virion – is usually spherical in shape and carries its genetic material on eight pieces of single stranded RNA known as segments. Each segment carries genes that encode for proteins that the virus needs in order to replicate inside the infected host cell. The genome is protected by a membrane envelope. Protruding from the virus envelope are hundreds of copies of two different varieties of viral glycoprotein spikes. The HA and NA surface proteins are involved in viral attachment and entry to host cells. They are also the main part of the virus recognized by our immune system as foreign, and most of the antibodies we make after infection are against these antigens.
The influenza virus changes often, so having flu caused by one strain does not give you full immunity to other strains.
- Widespread outbreaks of the flu usually follow significant changes (called antigenic shifts) in the virus and occur about every 10 years. People who get the flu tend to become much sicker when a shift in the flu virus occurs.
- Minor changes in the virus (called antigenic drifts) occur nearly every year.
The flu virus is extremely contagious and is transmitted from person to person by droplets expelled when sneezing and coughing. It can also be transmitted by direct contact, for example by touching virus-contaminated surfaces such as door handles and then touching the eyes or nose. Good hygiene practices, such as correct hand washing, are very important in preventing infection.
Risk Factors –
- Age – Seasonal influenza tends to target young children and older adults.
- Living conditions – People who live in facilities along with many other residents, such as nursing homes or military barracks, are more likely to develop influenza.
- Weakened immune system – Cancer treatments, anti-rejection drugs, corticosteroids and HIV/AIDS can weaken your immune system. This can make it easier for you to catch influenza and may also increase your risk of developing complications.
- Chronic illnesses – Chronic conditions, such as asthma, diabetes or heart problems, may increase your risk of influenza complications.
- Pregnancy – Pregnant women are more likely to develop influenza complications, particularly in the second and third trimesters.
- Obesity – People with a BMI of 40 or more have an increased risk of complications from flu.
Types of Influenza Virus
- Type A flu or influenza A viruses are capable of infecting animals, although it is more common for people to suffer the ailments associated with this type of flu. Wild birds commonly act as the hosts for this flu virus. Type A flu virus is constantly changing and is generally responsible for the large flu epidemics. The influenza A2 virus (and other variants of influenza) is spread by people who are already infected. The most common flu hot spots are those surfaces that an infected person has touched and rooms where he has been recently, especially areas where he has been sneezing.
- Type B – Unlike type A flu viruses, type B flu is found only in humans. Type B flu may cause a less severe reaction than type A flu virus, but occasionally, type B flu can still be extremely harmful. Influenza type B viruses are not classified by subtype and do not cause pandemics.
- Type C – Influenza C viruses are also found in people. They are, however, milder than either type A or B. People generally do not become very ill from the influenza type C viruses. Type C flu viruses do not cause epidemics.
Symptoms
It is common to confuse flu with a bad cold. Flu and cold symptoms may include a runny/blocked nose, sore throat, and cough. Here are some symptoms which a person with flu will have (note that these are not common heavy cold symptoms) –
- High temperature
- Cold sweats, shivers
- Headache
- Aching joints, aching limbs
- Fatigue, feeling utterly exhausted
- Gastro-intestinal symptoms, such as nausea, vomiting, and diarrhea, are much more common among children than adults
These symptoms may linger for about a week. The feeling of tiredness and gloom can continue for several weeks.
Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.
Treatment
The single best way to prevent the flu is to get a flu vaccine each season. There are several flu vaccine options for the 2015-2016 flu season.
Traditional flu vaccines made to protect against three different flu viruses (called “trivalent” vaccines) are available. In addition, flu vaccines made to protect against four different flu viruses (called “quadrivalent” vaccines) also are available.
Trivalent flu vaccine protects against two influenza A viruses (an H1N1 and an H3N2) and an influenza B virus.
There are two ways of tackling the disease – treating the symptoms and attacking the virus. The symptoms can be alleviated with drugs to reduce fever and pain such as paracetamol.
Antiviral drugs can be effective against influenza but must be administered within the first 2 days of symptoms appearing. Drugs such as oseltamivir (Tamiflu) attack the virus by inhibiting the enzyme neuraminidase and therefore prevent the virus from infecting cells.
Antibiotics are not used to treat influenza because they work by inhibiting bacterial cell wall production and protein synthesis and block cell metabolism and have no effect on viruses. They can be used to treat secondary bacterial infections.
Zanamivir and oseltamivir can cause mild side effects, including nausea and vomiting; zanamivir, which is inhaled, can cause difficulty breathing in some cases. Diarrhea is the most common side effect of peramivir. Most people are able to continue the medicine despite the side effects.
Alternative Treatment
Enchinacca – It is used to prevent or treat colds, influenza and other types of infections and is very helpful in stimulating the immune system.
Zinc – Studies suggest that use of zinc lozenges in the treatment and prevention of common cold and sore throat is very effective.
Vitamin D – Vitamin D plays a role in immune function. It has been suggested that the decline in vitamin D levels that occurs during the winter months might explain the higher incidence of influenza in the winter than at other times
Vitamin C – Vitamin C has been shown to inactivate influenza virus in test tubes. According to one practitioner, supplementing with massive doses of vitamin C can relieve symptoms and enhance recovery in patients with influenza.
Green and Black Tea – Green tea extract inhibited the growth of influenza virus in the test tube. This effect appeared to be due at least in part to epigallocatechin, one of the major catechin molecules in green tea.
N-Acetylcysteine – Oxidative stress appears to contribute to the lung damage that may result from influenza infection. N-acetylcysteine (NAC) is an antioxidant and is also a precursor to glutathione, which is one of the major antioxidants that occur naturally in lung tissue.
Sambucol – Sambucol, a proprietary preparation that contains extracts of black elderberries (Sambucus nigra L.) and raspberries (Rubus idaeus L.) inhibited the replication of influenza virus in the test tube. In addition, an extract of Sambucus nigra L. decreased the infectivity of human influenza virus H1N1 (the type that causes swine flu) in the test tube.
Astragalus (Astragulus membranaceus) – Used as an antiviral, an antiinflammatory, an immunomodulator, and an antioxidant.
Hyssop (Hyssop officinalis) – Used as an antiviral, an immunomodulator, and an expectorant.
Licorice (Glycyrrhiza glabra) – Used as an antiviral, an antiinflammatory, and an immunomodulator.
Lomatium (Lomatium dissectum) – Used as an antiviral, specifically for hard to treat respiratory tract infections.
Reference –
http://www.webmd.com/cold-and-flu/flu-guide/advanced-reading-types-of-flu-viruses
http://emedicine.medscape.com/article/219557-overview
http://www.medicalnewstoday.com/articles/15107.php
http://www.microbiologyonline.org.uk/media/transfer/doc/factfile_influenza.pdf
https://www.dhs.wisconsin.gov/publications/p4/p42064.pdf
http://www.mayoclinic.org/diseases-conditions/flu/basics/prevention/con-20035101
http://www.healthcommunities.com/common-cold/alternative-medicine/naturopathic-flu-treatment.shtml