Kenneth Agboifo WCH
Disease

Influenza

Causative agents

Influenza viruses belong to the family of viruses known as Orthomyxoviridae. They are negative single-stranded RNA viruses. These viruses can be sub-divided into three major classifications: A, B or C. Influenza viruses are enveloped (def) with a spherical or filamentous form. They are approximately 80-200 nanometers (def) in diameter. Influenza virus A and B are more common and virulent than type C. Influenza C mostly affect children younger than 6 years, causing respiratory infections.

Epidemiology
Influenza epidemiology is location dependent. It varies from one climate to the other. The disease is more prevalent in the winter. The northern and southern hemisphere experience winter at different times of the year. Consequently, there are two different flu seasons in a year. In the United States, influenza activities increase during the winter reaching a peak from December to March. This peak can vary, starting sometimes as early as October and extending to as late as May. The influenza season can become prolonged for places closer to the equator and could be an all year disease.

 Influenza and its complications can be life threatening. Children, imunocompromised (def) individuals and the elderly are more susceptible to it. The likelihood of children getting sick with influenza is three times that of adults. It kills about 250,000 to 500,000 people worldwide every year. Furthermore, it ranks seventh amongst the cause of death in the United States. The centers for disease control and prevention (CDC) estimates that influenza causes the hospitalization of about 200,000 people and death of about 36,000 people yearly in the United States.

Transmission

The influenza viruses attach and invade the epithelial cell of the upper respiratory track. It can be transmitted in the following ways;

Direct transmission: occurs when a person infected with influenza transfers mucus directly into the eyes, nose or mouth of a healthy person by coughing, sneezing and kissing.
Airborne route: when a healthy person inhales aerosolized droplets produced by someone infected with influenza. The aerosolized droplets are spread through coughing, spitting or sneezing by the infected person.
Contact transmission: occurs through indirect contact with the mucous membranes of an infected person. For example, through handshake, touching common surfaces contaminated with the influenza viruses, etcetera. This can be introduced to the mucous membrane of a healthy individual by hand-to-mouth, hand-to-eye or hand-to-nose contact.

Signs and symptoms

Influenza virus infection can present in several ways. Some of the signs and symptoms are listed below;

• Sudden onset of influenza can occur in some patients making it possible for them to tell the exact time the symptoms started.
• Chills or chilly sensations (shivering and shaking)
• Body temperature ranging from 38 to 39 degree centigrade
• Myalgia (def) may vary from mild to severe
• Cough
• Fatigue
• Sore throat
• Diarrhea and abdominal pain may be a feature in children but not normally a symptom in adults
• Rhinitis (def)
• Ocular symptoms such as irritated and watering eyes, photophobia (def) and burning sensations
• Severe headache
• Pharyngitis (def), tachycardia (def)

Some complications of influenza include;

• Pneumonia (primary or secondary bacteria pneumonia or from exacerbations of cardiopulmonary (def) conditions)
• Reye syndrome (def) occurs almost exclusively in children
• Acute coronary syndromes (def) increases during influenza season

Prevention and treatment

The transmission of influenza can be reduced or prevented  by;

• Practicing good personal hygiene like frequent handwashing with soap and water or alcohol based hand sanitizers.
• Staying at home when sick with influenza
• Covering mouth and nose when coughing or sneezing
• Sanitizing potentially contaminated surfaces
• Avoiding smoking ( smoking raises the risk of contracting influenza)
• Avoiding spitting in public areas

Vaccination against influenza is also a very effective preventive measure against influenza. It is especially recommended for high risk groups like children, immunocompromised (def) individuals and the elderly. Influenza vaccines are egg-based; the viruses are grown in fertilized hen egg. The most common vaccine is the inactivated (def) virus. However, the avirulent (def) virus can also be given as a life vaccine. Once vaccinated, it takes about two weeks for the vaccine to become effective.

There are two types of antiviral drugs used to treat influenza. They are:

Neuraminidase inhibitors: include Zanamivir (Relenza) and Oseltamivir (Tamiflu). They are sialic acid (def) analogue designed to halt viral spread in the body. They are able to do this by inhibiting the viral neuraminidases. They bind competitively with the active enzyme site of influenza A and B viruses.

M2 inhibitors: include Amatadine and Rimantadine. They are antiviral drugs that work by blocking the viral M2 protein (def) ion channel. This prevents the virus from infecting cells. However, they are only effective against influenza A. Influenza B lacks M2 molecule. Therefore, the drug is not effective against them. Nevetheless, these drugs are no longer recommended for the treatment of influenza because the virus has developed resistance against them.
 

Bibliography

• Leblebiciouglu,H. and Brook, I. (2009, August). Influenza. Retrieved March 26,2010, from http:emedicine.medscape.com/article/972269-print.
• Derlet W.R. and Sandrock C.E. (2009, December). Influenza. Retrieved March 26,2010, from http:emedicine.medscape.com/article/219557-print.
• National Institute of Allergy and Infectious Diseases. (n.d.) Influenza. Retrieved March 30,2010,from http://www3.niaid.nih.gov/topics/flu/understandingflu/definitionsoverview.htm
• Wikipedia (n.d.) Influenza. Retrieved March 26, 2010 from http://en.wikipedia.org/wiki/InfluenzaWikipedia (n.d.) Influenza A Virus. Retrieved March 26, 2010 from http://en.wikipedia.org/wiki/Influenza_A_virus
• Wikipedia (n.d.) Influenzavirus B. Retrieved March 26, 2010 from http://en.wikipedia.org/wiki/Influenzavirus_B