The flu is nothing to sneeze at

The flu is a disease of the respiratory system involving the mouth, nose, throat and occasionally the bronchi and lungs.

It is caused by a group of influenza viruses that are highly contagious, spread easily and infect humans. Influenza gets its name from medieval European times when it was widely believed that the position of the stars “influenced” the occurrence of these infectious pandemics.

According to the World Health Organization, influenza typically affects 5% to 15% of the general population. That means about one billion people per year around the world get the flu. In Canada between 10% and 15% or adults and 20% to 30% of children get the flu annually. It is estimated to cause 12,200 hospitalizations and about 3,500 deaths per year. Those infections tend to occur in late fall, winter and early spring, in part, due to the greater contact between humans that occur at this time.

The flu virus is made up of 35 to 40 different proteins that make the viral capsule, cell surface markers and enzymes involved in viral replication.

Influenza viruses have seven or eight different single strands of RNA (ribonucleic acid) inside each virus. The viral RNA hijacks the host genetic machinery to make copies of viral proteins, then reassembles inside the host cell and then leaves to infect more cells and replicate itself.

There are four groups of viruses, called influenza A, B, C and D. They are based on viral surface markers or proteins that are common to one of the groups. Influenza A is the most common group and tends to be the cause of pandemics when they occur. Influenza B and C are less common and less severe than group A. Influenza D does not occur in humans.

Virologists further classify the flu virus according to two cell surface markers, or proteins, known as H and N. H stands hemagglutinin and N stands for neuraminidase. Hemaglutinen is a gatekeeper protein that allows the virus into a host cell. It allows the binding of the virus to the cell surface and allows it to enter the host. Neuraminidase is also a gatekeeper protein that allows the virus out of the host cell so it can spread to other cells.

There are 18 different subtypes of H proteins and 11 different subtypes of N proteins. All subtypes have been identified in birds and other animals. Only three specific H proteins and two N proteins have been identified in humans.

These viruses can stay viable for up to 48 hours and can be transmitted to the oropharynx after sometimes touching a contaminated surface.

The common symptoms of influenza infection include sore throat, cough, nasal congestion, fatigue, fever, headaches, muscle aches, nausea and occasionally diarrhea. These infections typically last for five to 10 days but can last longer in some individuals. A residual cough can persist for several weeks after the infection has abated.

The incubation time for the flu is usually one to three days. That means that from first exposure to the virus to the development of symptoms, it can be 24 to 72 hours. Viral shedding can occur one or two days before symptoms occur and five to seven days after symptoms start. Viruses are typically spread in aerosolized droplets and secretions of the mouth and nose. That can occur when an infected person is normally breathing. Greater concentration occurs when a person sneezes or coughs.

The flu is usually a self-limited disease that gets better after one or two weeks. Those at risk for serious illness include children under the age of five, the elderly over the age of 65, individuals with comorbid conditions that lower the immune system including individuals with cancer and pre-existing heart, kidney and lung disease.

The flu vaccine usually is a mixture of three different dominant strains that are believed to be the most prevalent in the upcoming year. Flu vaccines are about 20% to 60% effective in matching the dominant strains. Vaccinations are recommended for those at high risk for developing serious illness and those who come in contact with vulnerable individuals.

Washing your hands frequently, covering your mouth and nose when sneezing or coughing, staying home when sick, drinking plenty of fluids and getting rest are commonly recommended to aid in flu recovery and preventing infection to others. Analgesics, anti-inflammatories and decongestants provide some symptomatic relief but do not affect the course and duration of infection.

Tamiflu and Relenza are two newer antiviral medicines that can be effective in preventing serious flu infection and aiding quicker recovery. Those drugs target the N protein that prevents viral spread.

Gargling with salt water and using a saline nasal irrigation can prevent viral binding to mucous membranes. Chicken noodle soup and spices like cayenne pepper, garlic and ginger can also help the immune system. Vitamin A, C, D and zinc can all have antiviral effects. Echinacea, elderberry, goldenseal, oregano oil and other herbs have also been recommended for flu infection.

The information provided in this article is not intended to constitute medical advice. All information and content are for general information purposes only.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.