Everything about the Influenza virus!
Date: 2 سال قبل
author: AmirAbad
The
influenza viruses are characterized by segmented RNA genomes requiring an RNA-dependent RNA
polymerase of viral origin for replication. The particular structure of the
influenza virus genome and function of its viral proteins enable antigenic
drift and antigenic shift. Influenza virus is in the virus family
Orthomyxoviridae.
The
Influenza A and B consists of eight segments of linear , single-stranded RNA.
The multipartite genome is encapsidated, each segment in a separate
nucleocapsid, and the nucleocapsids are surrounded by one envelope.
Influenza
A and B are major causes of respiratory infection.
Influenza
A viruses are classified into many subtypes based on specific proteins on the
surface of the virus. As influenza viruses circulate, they undergo genetic
changes that can affect their infectiousness and severity.
Influenza
C and influenza D viruses have only seven RNA segments and do not seem to cause
substantial disease in humans. However, influenza C virus infections can cause
influenza-like illness and hospitalizations in some instances, especially in
children. Influenza D viruses mainly affect cattle and do not seem to infect
humans.
What
Is Influenza?
Influenza
is a respiratory disease caused by infection with the influenza type A, B, C or
D virus. Influenza viruses are spread among people primarily through airborne
droplets released when you talk, cough, or sneeze.
Influenza
A and influenza B are the only types of influenza that can cause seasonal flu
epidemics.
The
flu is a common disease that is believed to affect around 8% of people in any
given year. Flu viruses tend to spread more frequently during colder months and
can lead to local seasonal epidemics.
Symptoms
Flu
symptoms can range from mild to severe, and they vary from person to person.
Common
symptoms of the flu include:
· fatigue
· nasal
congestion
· a
cough
· headaches
· a
sore throat
· body
aches
· chills
· a
fever
· vomiting
or diarrhea, which are more common in children
Some
people experience severe symptoms, which can include:
· chest
pain
· shortness
of breath
· severe
pain
· severe
weakness
· a
high fever
· seizures
· severe
dizziness
· loss
of consciousness
A
person who experiences any severe symptom should receive medical attention.
For
most people, flu symptoms are mild and short-lived. In others, though, the flu
can cause life-threatening complications. Children, older adults, pregnant
women, and people with certain coexisting medical problems are at a higher risk
of serious complications from an influenza virus infection.
Prevalence
According
to researchersTrusted Source, influenza A viruses are responsible for about 75%
of confirmed flu cases, while influenza B viruses are behind approximately 25%
of confirmed cases.
Severity
For
a person who is generally healthy, the flu is not typically dangerous. However,
it can severely affect certain groups of people, who should seek medical
attention as soon as they suspect that they have flu symptoms.
Those
most at riskTrusted Source of developing flu complications include:
· women
who are pregnant
· people
with certain chronic medical conditions
· children
younger than 5
· adults
aged 65 or over
Many
people believe that influenza A is more severe than influenza B. However, this
is not always the case.
Prevention
The
following can help prevent a person from catching or spreading the flu:
· limiting
contact with sick people
· staying
home when ill
· covering
the nose and mouth when sneezing or coughing
· washing
the hands often
· disinfecting
surfaces that may contain flu germs
· avoid
touching the eyes, nose, and mouth
· wearing
a mask when leaving the house
· The
best method of prevention is to receive a flu vaccination every year. The flu
vaccine can come as an injection or a nasal spray.
According
to a 2017 studyTrusted Source, the vaccine may reduce the risk of in-hospital
deaths from the flu, prevent associated intensive care unit hospitalization,
and reduce the duration of related hospital stays.
A
flu vaccine is developed every year based on the strains of influenza viruses
that are expected to be circulating most widely in the colder months.
Vaccination can reduce the impact of the flu but is not 100% effective. As a
result, diagnosis and treatment of influenza can be important for many people.
Types
of Influenza Tests
The
first step in diagnosing influenza is almost always a physical examination that
includes a review of any active flu-like symptoms. During seasonal flu
epidemics, additional testing beyond a physical exam may not be needed to
diagnose influenza.
When
other tests are needed, they focus on identifying signs of an influenza
infection. There are several different tests that can check for the presence of
an influenza virus. The choice of which test to prescribe depends on the
purpose of testing, how quickly results are needed, test availability, and
laboratory capabilities.
Antigen
test: Antigen tests use a sample from the
respiratory tract and look for antigens of an influenza virus. Antigens exist
on the surface of the virus and trigger an immune response. The presence of
influenza antigens can be an indication of an active flu infection.
Molecular
flu test: Molecular flu tests look for traces of
genetic material, or DNA, from the influenza virus in a sample from your
respiratory tract. These may also be called nucleic acid amplification tests
(NAATs) or referred to by a specific laboratory method, such as reverse
transcription polymerase chain reaction, (RT-PCR).
Serology
test: Serology tests look for antibodies to
influenza viruses in a blood sample. Antibodies are developed as part of the
immune system’s reaction to a viral infection. It can take time for antibodies
to form, though, so serology tests are used to identify a prior infection.
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