Seasonal Flu

• Seasonal influenza is an acute viral infection that is easily spread from person to person.
• Seasonal influenza viruses circulate around the world and can infect anyone of any age.
• Seasonal influenza viruses cause annual epidemics that peak during winter in temperate climates.
• Seasonal influenza is a serious public health problem that causes severe illness and death in high-risk populations.
• Influenza epidemic can have an economic burden due to the decrease in the efficiency of the workforce during the disease and the pressure it puts on the health system.
• Influenza vaccination is the most effective way to prevent infection.
• Antiviral drugs are available to treat influenza, however, influenza viruses can become resistant to these drugs.

Overview
Seasonal influenza is an acute viral infection caused by the influenza virus.
There are 3 types of seasonal influenza virus, which are: CBA 
type A is classified into subgroups based on the composition of surface proteins of the virus.
Among the large number of subgroups of influenza A viruses, types A(H₁N₁) and A(H₃N₂) are currently circulating in the human population.
Influenza viruses are circulating in all parts of the world.
Type C is much less common than A and B. For this reason, only type A and B viruses are used in making seasonal influenza vaccines.

The characteristics of seasonal flu include the sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, feeling weak and uncomfortable (a person feels unwell), sore throat and runny nose. The cough can be severe and last for 2 weeks or more.
Most people get rid of fever and other symptoms within a week without needing medical attention.
But the flu can cause severe illness or death, especially in high-risk groups (described below).
The time between being infected with the virus and the onset of the disease (which is known as the latent period of the disease) is approximately 2 days.
Who is considered a high-risk group?
Every year, influenza epidemics can seriously affect the entire population, but the highest risk of complications from influenza is in children under 2 years old, people aged 65 and older, pregnant women and people of any age who are medically unwell. For example, people with chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes) or people with a weakened immune system are seen.
The transmission of
seasonal influenza is easily spread and can spread in schools, nursing homes, business centers or small towns. When an infected person coughs, tiny droplets infected with the virus are released into the air, and if another person they If he breathes it, he will get sick. Also, the virus can be transmitted through hands infected with the influenza virus.
In order to prevent the transmission of the virus, people should cover their mouth and nose with a tissue when coughing and wash their hands regularly.

In countries with a temperate climate (northern or southern hemisphere), seasonal epidemics usually occur during winter, while in tropical regions, influenza occurs throughout the year and causes
unexpected problems.
Influenza can be seen in all parts of the world and annually 5-10% of adults and 20-30% of children are infected with it.
The disease can lead to hospitalization and death, especially among high-risk populations (children, the elderly, or people with chronic diseases).
It is also estimated that worldwide these epidemics result in 3 to 5 million severe cases of illness and 250,000 to 500,000 deaths annually.
In industrialized countries, most deaths related to influenza have been seen in people aged 65 years and older.
Epidemics can lead to widespread absenteeism from work and school and reduced productivity.
During peak disease periods, clinics and hospitals suffer from a heavier burden.
The exact effects of seasonal influenza epidemics in developing countries are not known, but research estimates indicate that a high percentage of children in developing countries die each year due to influenza-related causes.
Prevention
is the most effective way to prevent disease or severe consequences caused by disease, vaccination.
Safe and effective vaccines are available and have been used for over 60 years. .
In healthy adults, influenza vaccine provides adequate protection.
However, in the elderly, the influenza vaccine may be less effective in preventing the disease, but it reduces the severity of the disease and the possibility of morbidity and mortality.
Vaccination is especially important for people who are at risk of serious problems from the flu and people who live with or care for this group of people.
The World Health Organization recommends annual vaccination for the following groups.

• Pregnant women at any stage of pregnancy
• Children 6 months to 5 years old
• Elderly people (65 years and above)
• People with chronic diseases
• Health department staff

Influenza vaccination is most effective when the circulating viruses match the vaccine viruses.
Influenza viruses are constantly changing.
The WHO Global Influenza Surveillance and Response System (GISRS),
which works with national influenza centers around the world, observes and monitors influenza viruses circulating in humans.
For many years, the World Health Organization has announced its recommendations for the strains in the vaccine twice a year, which include 3 strains (in vaccines containing 3 strains) that are circulating more than other strains (containing two strains of Type A virus and a type B strain). With the start of the Northern Hemisphere influenza season in 2013-2014, quadrivalent vaccines containing an additional type B strain in addition to the strains included in the trivalent vaccine were recommended.
4-strain vaccines are expected to provide better protection against infections caused by influenza B virus. Anti-influenza drug
treatment
is available in some countries and can be effective in reducing serious complications and mortality from influenza.
Ideally, these drugs should be administered early (within 48 hours of the onset of symptoms).
There are two groups of these drugs:

1. Adamantanes include amantadine and rimantadine
2. Neuraminidasevir inhibitors (seltamivir, zanamivir, and in addition pramivir and lalina mevirke are available in several countries).

Some influenza viruses show resistance to antiviral drugs, which reduces the effectiveness of these drugs in treatment.
The World Health Organization observes and evaluates the susceptibility to antiviral drugs in circulating influenza viruses to
provide timely guidelines for the use of antiviral drugs in clinical control and pharmacoprevention.
The World Health Organization’s response
The World Health Organization and its partner organizations observe and monitor influenza globally, and recommend seasonal influenza vaccine strains twice a year (for the Northern Hemisphere and the Southern Hemisphere).
It also supports its members’ efforts to develop prevention and control strategies.
The World Health Organization also works to strengthen the capacities of influenza diagnosis at the national and regional levels.
These activities include observing and checking the sensitivity to antiviral drugs, checking and evaluating the disease, responding during outbreaks, and increasing vaccination coverage in high-risk groups.
Currently, the World Health Organization recommends neuraminidase inhibitors as the first line of treatment for people who need antiviral drugs.
Because influenza viruses that are currently circulating have shown resistance to adamantane.