QUELIMANE GENERAL SECONDARY SCHOOL

English Work

Grade 12

group: B

Topic: Influenza

Quelimane

2025

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 QUELIMANE GENERAL SECONDARY SCHOOL

Students: The Teacher:

Abacar João Paulo Sinate

Amina Taiobo

Anésio Lucas

Caldino Bacar

Carmélio Carlos

Dionízia Dinis

Dirosa Agostinho

Ermelinda Patrício

Eunice Francisco

Filton Feliciano

Francisco Cassamo

Jardel Carlos

Liliana Neto

Quina Tomarinho

Rosa João

Rosaria Rui

Sara Francisco

Zunaira Xavier

Quelimane

2025

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Índice

Introduction ................................................................................................................................ 4

What is influenza? ...................................................................................................................... 5

INFLUENZA VIRUS A ............................................................................................................. 6

INFLUENZA VIRUS B ............................................................................................................. 7

INFLUENZA VIRUS C ............................................................................................................. 7

Signs and symptoms ................................................................................................................... 9

Who catches influenza? ............................................................................................................ 10

Prevention -Vaccination ........................................................................................................... 10

How do you catch influenza? ................................................................................................... 10

How infectious is influenza? .................................................................................................... 10

How serious is influenza? ......................................................................................................... 10

How can you treat someone with influenza? ............................................................................ 11

What information is available about the vaccine? .................................................................... 11

How can you reduce the risk of influenza transmission in hospitals? ...................................... 12

Conclusion ................................................................................................................................ 14

References ................................................................................................................................ 15

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Introduction

Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza
viruses. It primarily affects the nose, throat and lungs and can range in severity from mild to
severe, sometimes leading to hospitalization or death, especially in vulnerable populations
such as the elderly, young children and individuals with weakened immune systems.

There are four main types of influenza viruses: A, B, C and D. influenza A and B viruses are
responsible for the seasonal flu epidemics that occur almost every winter, while influenza C
causes milder respiratory symptoms and influenza D primarily affects cattle.

The virus spreads through respiratory droplets when an infected person coughs, sneezes or
talks. Symptoms typically include fever, cough, sore throat, muscle aches, fatigue and chills.
Annual vaccination is the most effective way to prevent the flu and its complications, along
with good hygiene practices like regular hand washing and avoiding close contact with
infected individuals.

Influenza A viruses are further classified into subtypes based on two surface proteins:
hemagglutinin (H) and neuraminidase (N). Examples include H1N1 and H3N2. Influenza B
viruses are categorized into two main lineages: B/Yamagata and B/Victoria. While most
healthy individuals recover from the flu within a week or two without lasting effects, serious
complications such as pneumonia, bronchitis, sinus infections and worsening of chronic
medical conditions can occur.

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What is influenza?

Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of
the family Orthomyxoviridae (the influenza viruses), that affects birds and mammals. The
most common symptoms of the disease are chills, fever, sore throat, muscle pains, severe
headache, coughing, weakness/fatigue and general discomfort. Although it is often confused
with other influenza-like illnesses, especially the common cold, influenza is a more severe
disease than the common cold and is caused by a different type of virus. Influenza may
produce nausea and vomiting, particularly in children, but these symptoms are more common
in the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu".

Typically, influenza is transmitted through the air by coughs or sneezes, creating aerosols
containing the virus. Influenza can also be transmitted by direct contact with bird droppings or
nasal secretions, or through contact with contaminated surfaces. Airborne aerosols have been
thought to cause most infections, Influenza viruses can be inactivated by sunlight,
disinfectants and detergents. As the virus can be inactivated by soap, frequent hand washing
reduces the risk of infection.

Influenza spreads around the world in seasonal epidemics, resulting in the deaths of between
250,000 and 500,000 people every year, up to millions in some pandemic years.

Three influenza pandemics occurred in the 20th century and killed tens of millions of people,
with each of these pandemics being caused by the appearance of a new strain of the virus in
humans. Often, these new strains appear when an existing flu virus spreads to humans from
other animal species, or when an existing human strain picks up new genes from a virus that
usually infects birds or pigs. An avian strain named H5N1 raised the concern of a new
influenza pandemic,

Vaccinations against influenza, The most common human vaccine is the trivalent influenza
vaccine (TIV) that contains purified and inactivated antigens against three viral strains.
Typically, this vaccine includes material from two influenza A virus subtypes and one
influenza B virus strain.

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Antiviral drugs can be used to treat influenza, with neuraminidase inhibitorsbeing particularly
affect Structure of the influenza virion. The hemagglutinin (HA) and neuraminidase (NA)
proteins are shown on the surface of the particle. The viral RNAs that make up the genome
are shown as red coils inside the particle and bound to Ribonuclear Proteins (RNPs).

In virus classification influenza viruses are RNA viruses that make up three of the five genera
of the family Orthomyxoviridae:

 Influenza virus A
 Influenza virus B
 Influenza virus C

INFLUENZA VIRUS A

This genus has one species, influenza A virus. Wild aquatic birds are the natural hosts for a
large variety of influenza A. Occasionally; viruses are transmitted to other species and may
then cause devastating outbreaks in domestic poultry or give rise to human influenza
pandemics. The type A viruses are the most virulent human pathogens among the three
influenza types and cause the most severe disease. The influenza A virus can be subdivided
into different serotypes based on the antibody response to these viruses. The serotypes that
have been confirmed in humans, ordered by the number of known human pandemic deaths,
are:

 H1N1, which caused Spanish Flu in 1918, and Swine Flu in 2009
 H2N2, which caused Asian Flu in 1957
 H3N2, which caused Hong Kong Flu in 1968
 H5N1, which caused Bird Flu in 2004.
 H7N7, which has unusual zoonotic potentiaL
 H1N2, endemic in humans, pigs and birds
 H9N2
 H7N2
 H7N3
 H10N7

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INFLUENZA VIRUS B

This genus has one species, influenza B virus. Influenza B almost exclusively infects humans
[and is less common than influenza A.

INFLUENZA VIRUS C

This genus has one species, influenza C virus, which infects humans, dogs and pigs,
sometimes causing both severe illness and local epidemics However, influenza C is less
common than the other types and usually only causes mild disease in children Structure,
properties, and subtype nomenclature Influenza viruses A, B and C are very similar in overall
structure. The virus particle is 80–120 nanometres in diameter and usually roughly spherical,
although filamentous forms can occur.

These are made of a viral envelope containing two main types of glycoproteins, wrapped
around a central core. The central core contains the viral RNA genome and other viral
proteins that package and protect this RNA. RNA tends to be single stranded but in special
cases it is double.

Unusually for a virus, its genome is not a single piece of nucleic acid; instead, it contains
seven or eight pieces of segmented negative-sense RNA, each piece of RNA containing either
one or two genes. Hemagglutinin (HA) and neuraminidase (NA) are the two large
glycoproteins on the outside of the viral particles. HA is a lectin that mediates binding of the
virus to target cells and entry of the viral genome into the target cell, while NA is involved in
the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral
particles.

Thus, these proteins are targets for antiviral drugs. Furthermore; they are antigens to which
antibodies can be raised. Influenza A viruses are classified into subtypes based on antibody
responses to HA and NA. These different types of HA and NA form the basis of the H and N
distinctions in, for example, H5N1. There are 16 H and 9 N subtypes known, but only H 1, 2
and 3, and N 1 and 2 are commonly found in humans.

The Viruses can replicate only in living cells. Influenza infection and replication is a multi-
step process: First, the virus has to bind to and enter the cell, then deliver its genome to a site
where it can produce new copies of viral proteins and RNA, assemble these components into
new viral particles, and, last, exit the host cell.

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Influenza viruses bind through hemagglutinin onto sialic acid sugars on the surfaces of
epithelial cells, typically in the nose, throat, and lungs of mammals, and intestines of birds.

After the hemagglutinin is cleaved by a protease, the cell imports the virus by endocytosis.

Once inside the cell, the acidic conditions in the endosome cause two events to happen: First,
part of the hemagglutinin protein fuses the viral envelopewith the vacuole's membrane, then
the M2 ion channel allows protons to move through the viral envelope and acidify the core of
the virus, which causes the core to dissemble and release the viral RNA and core proteins.

The viral RNA (vRNA) molecules, accessory proteins and RNA-dependent

RNA polymerase is then released into the cytoplasm (Stage 2). The M2 ion channel is
blocked by amantadine drugs, preventing infection.

These core proteins and vRNA form a complex that is transported into the cell nucleus, where
the RNA-dependent RNA polymerase begins transcribing complementary positive-sense
vRNA (Steps 3a and b). The vRNA either is exported into the cytoplasm and translated (step
4) or remains in the nucleus. Newly synthesised viral proteins are either secreted through the
Golgi apparatus onto the cell surface (in the case of neuraminidase and hemagglutinin, step
5b) or transported back into the nucleus to bind vRNA and form new viral genome particles
(step 5a). Other viral proteins have multiple actions in the host cell, including degrading
cellular mRNA and using the released nucleotides for vRNA synthesis and also inhibiting
translation of host-cell mRNAs.

Negative-sense vRNAs that form the genomes of future viruses, RNAdependent RNA
polymerase, and other viral proteins are assembled into a virion. Hemagglutinin and
neuraminidase molecules cluster into a bulge in the cell membrane. The vRNA and viral core
proteins leave the nucleus and enter this membrane protrusion.

The mature virus buds off from the cell in a sphere of host phospholipid membrane, acquiring
hemagglutinin and neuraminidase with this membrane coat (step 7). As before, the viruses
adhere to the cell through hemagglutinin; the mature viruses detach once their neuraminidase
has cleaved sialic acid residues from the host cell.

Drugs that inhibit neuraminidase, such as oseltamivir, therefore, prevent the release of new
infectious viruses and halt viral replication. After the release of new influenza viruses, the
host cell dies. Because of the absence of RNA proofreading enzymes, the RNA-dependent
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RNA polymerase that copies the viral genome makes an error roughly every 10 thousand
nucleotides, which is the approximate length of the influenza vRNA. Hence, the majority of
newly manufactured influenza viruses are mutants; this causes antigenic drift, which is a slow
change in the antigens on the viral surface over time. The separation of the genome into eight
separate segments of vRNA allows mixing or reassortment of vRNAs if more than one type
of influenza virus infects a single cell. The resulting rapid change in viral genetics produces
antigenic shifts, which are sudden changes from one antigen to another. These sudden large
changes allow the virus to infect new host species and quickly overcome protective immunity.

Signs and symptoms

Most sensitive symptoms for diagnosing influenza] Symptom:

 Fever;
 Cough;
 Nasal;
 Fever and extreme coldness (chills shivering, shaking (rigor));
 Cough;
 Nasal congestion;
 Body aches, especially joints and throat;
 Fatigue;
 Headache;
 Irritated, watering eyes;
 Reddened eyes, skin (especially face), mouth, throat and nose;
 In children, gastrointestinal symptoms such as diarrhea and abdominal pain (may be
severe in children with influenza B);
 Congestion.

Common symptoms of the flu such as fever, headaches, and fatigue are the result of the huge
amounts of pro inflammatory cytokines and chemokines (such as interferon or tumor necrosis
factor) produced from influenzainfected cells.]

In contrast to the rhinovirus that causes the common cold, influenza does cause tissue
damage, so symptoms are not entirely due to the inflammatory response.

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Who catches influenza?

Anyone can catch ‘flu; the highest rates of infection are usually in school age children.

Most influenza infections occur during the winter months.

The severity of illness occurring each year varies, depending on the particular strain that is
circulating. Some influenza viruses cause more severe illness than others. Therefore in some
winters people may feel more unwell with ‘flu than in other years.

Prevention -Vaccination

Vaccination against influenza with an influenza vaccine is often recommended for high-risk
groups, such as children and the elderly, or in people who have asthma, diabetes, heart
disease, or are immunecompromised. Prevention –Vaccination

How do you catch influenza?

For the most part, influenza is caught by breathing in air containing the virus after an infected
person coughs or sneezes, or by touching a surface where the virus has landed and then
touching your mouth or nose.

How infectious is influenza?

Influenza is very infectious and can spread rapidly from person to person. Some strains of the
virus are more infectious than others and some can cause more severe illness.

How serious is influenza?

Most people recover completely from influenza in a matter of days or a week. For other
groups, e.g. older people, pregnant women, those with other illnesses (such as chest or heart
disease, or diabetes) and newborn babies, influenza can be a serious illness. Serious illness
from influenza is very rare.

It can be caused either by the virus itself causing a severe viral pneumonia (inflammation of
the lungs, usually caused by an infection), or by triggering a bacterial infection causing
bronchitis and pneumonia, or a worsening of any underlying chronic medical condition such
as heart disease. It is important to remember that this does not always happen, but medical
advice must be sought if your symptoms worsen and you are in the above group of patients.

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How can you treat someone with influenza?

Most people with “flu” need no special treatment. Influenza is caused by a virus so antibiotics
do not help unless there is a complication. Occasionally a special ‘antiviral’ medicine is given
to people in the ‘at risk groups’ (see below) or those whose illness is getting worse.

Someone who is ill with flu should keep warm, rest and drink lots of fluids to prevent
dehydration.

Paracetamol can be given to reduce the fever. It is best to stay at home while feeling ill with
influenza as this reduces the chance of spreading the infection to others.

Advice can be sought from NHS Direct telephone lines if required. However it is important to
contact your GP if you have an underlying health condition and are worried about your
symptoms.

What information is available about the vaccine?

A vaccine is available to protect against ‘flu. Each year a new vaccine has to be produced to
protect against the ‘flu viruses expected to be in circulation that winter and to boost the
immune response (the way the body deals with infection).

The vaccine is very safe and side effects are uncommon and usually mild. The vaccine is
given in the autumn before the ‘flu season begins. It is not recommended for everyone, but it
is advisable for those likely to be more seriously affected by influenza (so called ‘at risk’
groups).

These include:

 People of any age with chronic heart, lung, neurological, metabolic disorders
(including severe asthma and diabetes), kidney problems or a lowered immune system
due to treatment or disease;
 Pregnant women;
 Everyone aged 65 years and over;
 Those in long stay residential care accommodation where influenza, once introduced,
may spread rapidly.

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It is recommended that immunization be offered to health and social care workers involved in
the direct care of and/or support to patients and also to anyone caring for a person in the ‘at
risk’ groups.

Children and fit adults under the age of 65 years, who are not in one of the groups mentioned
above, are not offered the vaccine as part of the national programmer.

How can you reduce the risk of influenza transmission in hospitals?

Patients with influenza should be isolated in a single room.

General advice:

 Wash hands frequently and carefully with soap and water and dry thoroughly;
 Avoid touching surfaces (such as door handles) and then the face;
 Cover your mouth and nose with a single-use tissue when coughing or sneezing and
dispose of used or dirty tissues in a bin - ‘Catch it, Bin it, Kill it’ and then wash and
dry your hands thoroughly.

For prospective patients:

 If you are due to attend an out-patient appointment and have ‘flu-like symptoms,
please contact the relevant out-patients department to discuss the possibility of re-
scheduling your appointment;
 If you are due to attend for surgery and have ‘flu-like symptoms, please contact the
relevant department or team;
 Usually patients who are in the ‘at risk’ groups are contacted by their GP to ensure
that their annual vaccination has been given (often in October).
 If you think you should have been vaccinated and have not been, but you are due for
admission to the hospital, please contact your GP surgery in good time before
admission to receive the vaccine. Being on the waiting list for surgery is not a contra-
indication for having the vaccine.

For visitors:

 People should not visit if they have had ‘flu-like symptoms in the previous 72 hours;
 Children should not visit patients with suspected flu and the number of visitors should
be limited to essential people only;

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  Visitors will be required to wear some protective clothing (this will be explained by
the ward staff), and should avoid going into the room while certain procedures are
being carried out.

For staff:

 Staff should remain off work until they are symptom-free or deemed to be no longer
infectious;

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Conclusion

In conclusion, influenza remains a significant global health challenge due to its high
transmissibility, potential for severe complications, and frequent viral mutations. While most
cases are mild and self-limiting, the flu can lead to serious illness, particularly in vulnerable
populations. Annual vaccination, good hygiene practices, and early antiviral treatment are key
strategies in reducing the impact of influenza. Continued public health efforts, research, and
global surveillance are essential to prevent outbreaks and manage future pandemics
effectively.

In summary, influenza is a highly contagious respiratory illness that poses ongoing health
risks worldwide. Its ability to mutate rapidly and evade immune defenses necessitates
constant monitoring and the development of updated vaccines each year. Although the
majority of infected individuals recover without complications, influenza can cause severe
illness and death especially among high-risk groups such as young children, the elderly,
pregnant women and individuals with chronic health conditions.

The burden of influenza extends beyond individuals health, impacting healthcare systems and
economies due to increased hospitalizations, medical costs and lost productivity. Therefore,
preventive measures-especially annual vaccination, public health education, and prompt
treatment-are critical in reducing the spread and severity of the disease.

Ongoing global surveillance, research into more effective and universal vaccines, and
improved access to healthcare are vital for controlling influenza outbreaks and preparing for
future pandemics. Through coordinated public health efforts, the global community can better
manage the seasonal impact of influenza and protect population.

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References

Influenza manual for community leaders and community health-workers;

www.vaers.hhs.gov or call 1-800-822-7967. VAERS is only for reporting reactions, and

www.HealthLinkBC.ca/more/resources/healthlink-bc-files

Royal Papworth Hospital NHS Foundation Trust Papworth Road Cambridge Biomedical
Campus Cambridge CB2 0AY Tel: 01223 638000 www.royalpapworth.nhs.uk A member of
Cambridge University Health Partner

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