Microbiology Lab

Done by : Yasmin El Helu Rana Abu Zuhri

Asmaa Abu Shamla

Respiratory tract

infection

Fungal infection of

the respiratory tract

Aspergillosis Is an allergic reaction, invasive infection or growth caused

by Aspergillus fumigatus. Inhaling of certain species of this fungi’s mold spores can

lead to dire consequences, particularly by those with weak immune systems.

Aspergillosis takes on different forms:-

Allergic bronchopulmonary aspergillosis allergic reaction to aspergillus, developing in those with pre-

existing lung problems, such as asthma or cystic fibrosis.

Invasive pulmonary aspergillosis

The most severe form of the disease by aspergillus mold spores. Almost exclusively affecting those with weakened immune

systems, this infection spreads rapidly. It comes with a high risk of invading and damaging tissue

throughout your body, especially your lungs , brain , heart and kidneys.

Aspergilloma

• Is a fungus ball, occurring in those who had a previous lung disease.

• Lungs that have air space damage caused by emphysema, tuberculosis, histoplasmosis, cystic fibrosis, sarcoidosis, lung cancer or other lung diseases develop pulmonary aspergilloma.

Histoplasmosis Is an infectious disease caused by inhaling the spores of a

fungus called Histoplasma capsulatum. Histoplasmosis is not contagious. Primarily affects a person's lungs, and its symptoms vary

greatly. The vast majority of infected people are asymptomatic , or can appear as a mild, flu-like respiratory illness .

People with weakened immune systems are at the greatest risk for developing severe and disseminated histoplasmosis.

Fungal Sinusitis Fungi involved in sinusitis include:• Aspergillus is the most common cause of all

forms of fungal sinusitis.• Other fungi include, Alternaria, Cryptococcus,

Candida, Sporothrix,, and Mucormycosis.

Thrush Is an oral infection with the fungus Candida albicans, which causes yellow, raised sores in the mouth, sometimes extending to the throat (cause of sore throat).

Bacterial infection of

the respiratory tract

Respiratory tract infection caused by Bacteria:-

1-Upper respiratory tract infections. 2- Otitis media 3-Lower respiratory tract infections. 4-Tuberculosis (TB).

• The upper respiratory tract: includes the sinuses, nasal passages, pharynx, and larynx.

• An upper respiratory tract infection : is an infectious process of any of the components of the upper airway.

Upper respiratory tract infection (URI): - Represents the most common acute illness evaluated in the

outpatient setting. Viruses account for most URIs. Bacteria account for up to 25 percent of upper respiratory

tract infections. Bacterial primary infection or superinfection may require

targeted therapy. Specific manifestations of URIs:- Rhinitis, pharyngitis, sinusitis, epiglottitis, laryngitis, and

tracheitis .

Pharyngitis :- Is defined as an infection or irritation of the pharynx and/or tonsils. The etiology is usually infectious:- 1- Viral origin, which is the most common cause. These cases are

benign and self-limiting for the most part. 2- Bacterial origin, which is self-limiting, but are concerning

because of suppurative and nonsuppurative complications. 3-Fungal origin

Non-infectiousallergy, trauma(mechanical, chemical or thermal irritation), toxins, and

neoplasia.

Bacteria causes pharyngitis:-1-Streptococcal pharyngitis Caused by group A beta hemolytic streptococcus (GAS)-(Streptococcus

pyogenes). The most significant bacterial agent causing pharyngitis in both adults and

children. Symptoms include fever ,sore throat,, and enlarged lymph node. It is the cause of 37% of sore throats among children. A definitive diagnosis is made based on the results of a throat culture

A culture positive case of streptococcal

pharyngitis with typical tonsillar

exudate in a 16 year old.

Note the redness and edema of the oropharynx, the

petechiae, or small red spots, on the

soft palate. This is an uncommon but highly specific

finding in streptococcal pharyngitis.

2-Fusobacterium necrophorum

• Are normal inhabitants of the oropharyngeal flora. • responsible for 10% of all acute sore throats , 21% of all

recurring sore throats, and 23% of peritonsillar abscesses• In 1 out of 400 untreated cases, Lemierre's syndrome occurs-

Known as (human necrobacillosis)- It’s a form of thrombophlebitis.

Fusobacterium necrophorum bacteria cultured in a thioglycollate medium for 48 hours.

F. necrophorum is a nonmotile, gram-negative anaerobe that normally inhabitants the pharynx, gastrointestinal tract, and

female genital tract .

• 3- Diphtheria life threatening upper respiratory infection caused by

Corynebacterium diphtheriae which has been largely eradicated in developed nations since the introduction of childhood vaccination programs, but is still reported in the Third Worldand increasingly in some areas in Eastern Europe.

• Clinical criteria Upper respiratory tract illness with sore throat Low-grade fever An adherent pseudomembrane of the tonsil(s), pharynx, and/or

nose.

Epiglottitis:- • Inflammation of the epiglottis , swelling of this structure can

interfere with breathing and constitutes a medical emergency . • The infection can cause the epiglottis to either obstruct or

completely close off the trachea.

• Caused by:- Haemophilus influenzae type B, although some cases are

attributable to Streptococcus pneumoniae , Streptococcus agalactiae, Staphylococcus aureus, and Streptococcus pyogenes

Acute H influenzae type b epiglottitis

with striking erythema and swelling of the

epiglottis.

`

Tracheitis:- Although the trachea is usually considered part of the lower respiratory tract, in

ICD-10 tracheitis is classified under "Acute upper respiratory infections".

Bacterial tracheitis• A bacterial infection of the trachea and is capable of

producing airway obstruction.• One of the most common causes is Staphylococcus aureus

and often follows a recent viral upper respiratory infection. • It is the most serious in young children, possibly because of

the relatively small size of the trachea that gets easily blocked by swelling.

Sinusitis

The bacteria most commonly implicated in sinusitis include:

• Streptococcus pneumoniae. This bacterium is found in up to 45% of adults and children with sinusitis.

• H. influenzae (a common bacterium associated with many upper respiratory infections). This bacterium causes about 25% of sinusitis cases in children.

• Moraxella catarrhalis. Over 75% of all children harbor this bacterium, which causes about 25% of sinusitis cases.

Other possible bacteria include:

• Other streptococcal strains• Staphylococcus aureus• P. aeruginosa, Klebsiella pneumoniae, Proteus

mirabilis, Enterobacter species, and Escherichia coli• Fusobacterium nucleatum and Prevotella intermedia)

...Go with

Rana

Bacterial lower

respiratory tract infections

Lower respiratory tract infection

• The lower respiratory tract consists of the trachea ,bronchial tubes, the bronchioles, and the lung.

• Lower respiratory tract infections are generally more serious than upper respiratory infections.

• LRIs are the leading cause of death among all infectious diseases.

• The most common LRIs are bronchitis, pneumonia, and empyema.

Acute Bronchitis

• Bronchitis is the inflammation of the mucus membranes of the bronchi.

• Usually caused by viruses and rarely by bacteria.

• Characteristic symptoms include cough, sputum production, shortness of breath ,wheezing.

• Bacteria like 1. mycoplasma pneumoniae, 2.streptococcus pneumoniae, 3.bordatella pertussis and 4.chlamydophila pneumoniae account for about 10% of acute cases .

• Diagnosis is by clinical examination and sometimes microbiological examination of the sputum.

• Treatment for acute bronchitis is

typically symptomatic, as viruses cause most cases of it, antibiotics should not be used unless microscopic examination of gram-stained sputum reveals large numbers of bacteria.

Chronic bronchitis• Chronic bronchitis, a type of chronic

obstructive pulmonary disease .

• Cigarette smoking is the most common cause, followed by air pollution and occupational exposure to irritants.

Pneumonia

• Pneumonia can be generally defined as inflammation of the lung parenchyma, in which consolidation of the affected part and a filling of the alveolar air spaces with exudate.

• Often pneumonia begins after an upper respiratory tract infection (an infection of the nose and throat) ,pneumonia begin after 2 or 3 days.

• Sign and symptoms: fever ,rigors ,cough, dyspnea ,chest pain, hemoptysis

Typical pneumonia• Streptococcus pneumoniae, or

pneumococcus, is Gram-positive, alpha-hemolytic, bile-soluble aerotolerant anaerobic member of the Streptococci.

• S. pneumoniae was recognized as a major cause of pneumonia.

Atypical pneumonia• The bacteria responsible for causing atypical pneumonia are: 1.Chlamydophila pneumoniae, 2.Mycoplasma pneumoniae and

3.Legionella pneumophila.• Most forms of atypical pneumonia are characterized by mild

symptoms; • However, the pneumonia caused by

Legionella sometimes result in severe symptoms. The mortality rate of Legionella induced pneumonia is quite high.

Community acquired pneumonia• Community acquired pneumonia : is the 4th most widespread

cause of fatality.• 85 percent of the CAP episodes occur due to typical pathogens

like 1.Haemophilus influenza, 2.Moraxella catarrhalis and 3.Streptococcus pneumoniae.

• The other 15 percent of the CAP cases occur due to atypical pathogens like 1.Legionella species, 2.Chlamydia pneumoniae and 3.Mycoplasma pneumoniae.

• In rare cases the condition can also be triggered by: 1.Acinetobacter, 2.Pseudomonas aeruginosa and 3.Enterobacter.

Hospital-Acquired Pneumonia • Develops at least 48 h after hospital

admission.

• The most common pathogens are :• 1.gram-negative bacilli mainly : Enterobacter

sp, Klebsiella pneumoniae, Escherichia coli, Serratia marcescens, Proteus sp, Acinetobacter sp.

• 2.Staphylococcus aureus, • 3. Haemophilus influenzae.

• Pseudomonas aeruginosa, which is especially common in pneumonias acquired in intensive care settings and in patients with cystic fibrosis, neutropenia, advanced AIDS, and bronchiectasis.

• Drug-resistant organisms are an important concern.

• Etiology: The most common cause is microaspiration of bacteria that colonize the oropharynx and upper airways in seriously ill patients.

Other types• Tuberculosis can cause pneumonia in some people,

especially those with a weak immune system.

• Pneumonia caused by Yersinia pestis is usually called pneumonic plague.

Diagnosis:• Chest x-ray and clinical criteria.• Sometimes bronchoscopy, blood cultures.

Treatment:• Empirically chosen antibiotics active against resistant gram-

negative and gram-positive organisms• If the diagnosis is suspected, treatment is with antibiotics

that are chosen empirically based on local sensitivity patterns.

Empyema• Is a collection of pus within a naturally existing anatomical

cavity, such as the lung pleura. • It must be differentiated from an abscess, which is a

collection of pus in a newly formed cavity.• Most pleural empyemas arise from an infection within the

lung ‘pneumonia’. However, it can also arise from 1.penetrating chest trauma, 2.esophageal rupture, 3.complication from lung surgery, 4.or inoculation of the pleural cavity after thoracentesis.

• Symptoms include: cough, fever, chest pain, sweating and shortness of breath, clubbing of the fingers.

• Diagnosis is confirmed by thoracentesis; pus may be aspirated from the pleural space.

• The pleural fluid typically has a leukocytosis, low pH ,low glucose ,a high LDH (lactate dehydrogenase), elevated protein and may contain infectious organisms.

TreatmentAppropriate antibiotic selection should be based on the Gram stain

and culture of the pleural fluid; however, because a large number

of patients may have already received antibiotics at the time of thoracentesis, an empiric selection of the most appropriate antibiotics

is necessary.

Otitis media• Inflammation of the middle ear.• It occurs in the area between the tympanic membrane

and the inner ear, including the eustachian tube.• The most common bacterial pathogen is

Streptococcus pneumoniae.• Others include 1.Pseudomonas aeruginosa,

2.nontypeable Haemophilus influenzae, and 3.Moraxella catarrhalis.

• Among older adolescents and young adults, the most common cause of ear infections is Haemophilus influenzae.

Tuberculosis• Tuberculosis (TB) is an

infectious disease caused by the bacteria Mycobacterium tuberculosis, and mycobacterium kanasasii, M.avium-intracellulare.

• TB disease most often affects the lungs, but can occur anywhere in the body

Symptoms• The most common symptom of contagious TB

disease is a cough that lasts for more than a three weeks, sometimes producing mucous and/or blood.

• Other symptoms may include fatigue, loss of appetite, weight loss, fever, and night sweats.

• Chest pain may also occur.

Diagnosis:• Tuberculosis is diagnosed by finding Mycobacterium

tuberculosis in a clinical specimen taken from the patient, either by acid fast stain or sputum culture(6 weeks).

• While other investigations may strongly suggest tuberculosis as the diagnosis, they cannot confirm it .

Treatment: • the standard "short" course treatment for TB is isoniazid,

rifampicin ,pyrazinamide, and ethambutol for two months, then isoniazid and rifampicin alone for a further four months.

...Go with Asmaa

Viral Infections of the Respiratory Tract

Made by:Asma’a Abu Shamlah

To:Dr. Ayham Abu Laila

• Respiratory tract infections are common in both adults and children.

• Most are probably viral induced -at least initially, and are fairly mild, self- limiting and confined to the upper respiratory tract (URT).

• However, in infants and children, URT infections may spread downwards and cause more severe infections and even death.

The respiratory tract infections are classified according the anatomic

division in to:1. upper respiratory tract infections (URTI)

which involve the airway above the glottis or vocal cords

(nose, sinuses, pharynx or larynx).

This commonly includes: rhinitis, sinusitis, tonsillitis,

pharyngitis, laryngitis, otitis media epiglottitis and the

common cold.

• Over 200 different viruses have been isolated in patients

with URIs. The most common virus is called the rhinovirus.

Other viruses include the coronavirus, parainfluenza virus,

adenovirus, enterovirus, and respiratory syncytial virus.

2. lower respiratory tract infections : which involve the trachea, bronchial tubes, the bronchioles, and the

lungs (below the glottis).• Lower respiratory infections, such as pneumonia and bronchitis ,

tend to be far more serious conditions than upper respiratory infections (such as the common cold) and are the leading cause of death among all infectious diseases.

Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.

1. Upper Respiratory Tract Viral Infections

Common Cold• The common cold (also known as nasopharyngitis or acute

viral rhinopharyngitis ) is the most frequent infectious disease in humans with the average adult contracting two to four infections a year and the average child contracting between 6–12.

• Common symptoms include a cough, sore throat, runny nose, nasal congestion and fever. Sometimes this may be accompanied by conjunctivitis (pink eye), muscle aches, fatigue, headaches, shivering, and loss of appetite.

• There is currently no known treatment that shortens the duration; however, symptoms usually resolve spontaneously in 7 to 10 days, with some symptoms possibly lasting for up to three weeks.

• Collectively, colds and other upper respiratory tract infections (URTI) with similar symptoms are included in the diagnosis of influenza-like illness.

• Due to the many different types of viruses and their tendency for continuous mutation, it is impossible to gain complete immunity to the common cold.

The causes of the common cold are:1. Rhinovirus which cases 30–50% of cases.2. Coronavirus causes 10–15% of cases.

• Human rhinovirus is a type of picornaviruses with 99 known serotypes. It is the most common viral infective agents in humans.

Rhinovirus infection proliferates in temperatures between 33–35 °C, and this may be why reproduction occurs primarily in the nose .

• Coronaviruses are enveloped viruses with a single-stranded RNA genome and a helical symmetry.

• Others causes of common cold include: influenza viruse (5–15%), human parainfluenza viruses, human respiratory syncytial virus, adenoviruses, enteroviruses, and metapneumovirus.

Tonsillitis Tonsillitis is an inflammation of the tonsils with symptoms

include :• red and/or swollen tonsils• white or yellow patches on the tonsils• tender, stiff, and/or swollen neck• sore throat with painful or difficult swallowing• cough, headache, sore eyes, body aches, otalgia, fever, chills

and nasal congestions.

Acute tonsillitis is caused by both bacteria and viruses with bacterial tonsillitis is quite common.

While no treatment has been found to shorten the duration of viral tonsillitis, bacterial causes are treatable with antibiotics.

The most common causes of viral tonsillitis are:• The common cold viruses (adenovirus, rhinovirus, influenza,

coronavirus, respiratory syncytial virus).

• It can also be caused by Epstein-Barr virus, herpes simplex virus, cytomegalovirus, or HIV.

Under normal circumstances, as viruses enter the body through the nose and mouth, they are filtered in the tonsils. Within the tonsils, white blood cells of the immune system mount an attack that helps destroy the viruses, and also causes inflammation and fever.

The infection may also be present in the throat and surrounding areas, causing inflammation of the pharynx.

Adenoviruses from family Adenoviridae are medium-sized nonenveloped icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome.

There are 55 serotypes in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well.

Human respiratory syncytial virus (RSV also called pneumovirus) is the major cause of lower respiratory tract infection (especially bronchiolitis) and hospital visits during infancy and childhood especially in the temperate climates.

• Natural infection with RSV induces protective immunity which wanes over time, and thus people can be infected multiple times.

• Severe RSV infections have increasingly been found among elderly patients.

• RSV is a single-stranded RNA virus of the family Paramyxoviridae, which includes common respiratory viruses such as those causing measles and mumps.

Epstein-Barr virus (EBV), also called human herpesvirus 4 (HHV-4), is a virus of the herpes family, which includes herpes simplex virus 1 and 2, and is one of the most common viruses in humans.

• Infants become susceptible to EBV as soon as maternal antibody protection disappears.

• It is associated with particular forms of cancer, from which is nasopharyngeal carcinoma, and there is evidence that infection with the virus is associated with a higher risk of certain autoimmune diseases.

• Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood.

Herpes simplex virus 1 and 2 (HSV-1 and HSV-2) are two members of the herpes virus family, Herpesviridae.

• The structure of herpes viruses consists of a relatively large double-stranded, linear DNA genome encased within an icosahedral capsid, which is wrapped in an envelope.

• Both HSV-1 (which produces cold sores) and HSV-2 (which produces genital herpes) are ubiquitous and contagious. They can be spread when an infected person is producing and shedding the virus.

• Sometimes, the viruses cause very mild or atypical symptoms during outbreaks. However, as neuroinvasive viruses, HSV-1 and -2 persist in the body by becoming latent and hiding from the immune system in the cell bodies of nerves.

Cytomegalovirus is also a viral genus of the Herpesviridae or herpesviruses family.

• The species that infects humans is commonly known as human CMV (HCMV) or human herpesvirus-5 (HHV-5). And like all herpesviruses share a characteristic ability to remain latent within the body over long periods.

• (Although they may be found throughout the body, CMV infections are frequently associated with the salivary glands) .

Sinusitis• Sinusitis is inflammation of the paranasal

sinuses, which may be due to infection, allergy, or autoimmune issues, but most cases are due to a viral infection. Drainage of mucous secretions in these spaces may be impaired and lead to secondary bacterial infection. This resolve over the course of 10 days.

It is a common condition, with roughly 90% of adults have had sinusitis at some point in their life .

By duration, sinusitis can be acute (going on less than four weeks), subacute (4–8 weeks) or chronic (going on for 8 weeks or more).

All three types of sinusitis have similar symptoms, and are thus often difficult to distinguish.

(Viral sinusitis typically lasts for 7 to 10 days, whereas bacterial sinusitis is more persistent.)

• Chronic sinusitis have symptoms of nasal congestion, facial pain, headache, night-time coughing and many others.

And By location, sinusitis can be frontal, ethmoid, maxillary and sphenoid sinuses.

The major causes of sinusitis are Adenovirus and Respiratory Syncytial Virus.

Pharyngitis (Sore Throat)• Pharyngitis is an inflammation of the throat

or pharynx. In most cases it is painful. It is the most common cause of a sore throat.

• Like many types of inflammation, pharyngitis can be acute – characterized by a rapid onset and typically a relatively short course – or chronic.

• Pharyngitis can result in very large tonsils which cause trouble swallowing and breathing. Pharyngitis can be accompanied by a cough or fever, for example, if caused by a systemic infection.

• Most acute cases are caused by viral infections (40–80%), with the remainder caused by bacterial infections, fungal infections, or irritants such as pollutants or chemical substances.

• If the inflammation includes tonsillitis, it is called pharyngotonsillitis. Another sub classification is nasopharyngitis (the common cold).

• The most common viral cause is adenovirus. Others are influenza Virus, Epstein-Barr virus, Herpes simplex virus and common cold viruses.

Laryngitis Laryngitis is an inflammation of the larynx. Symptoms are:• hoarse voice or the complete loss of the voice because of irritation to

the vocal folds (dysphonia).• Dry, sore throat• Coughing, which can be a symptom of, or a factor in causing laryngitis• Difficulty swallowing• Sensation of swelling in the area of the larynx• Cold or flu-like symptoms• Swollen lymph nodes in the throat, chest, or face• Fever• Coughing out blood• Difficulty breathing (mostly in children)• Difficulty eating• Increased production of saliva in mouth

• Laryngitis is categorized as acute if it lasts less than a few days. Otherwise it is categorized as chronic, and may last over 3 weeks.

• The chronic form of disease occurs mostly in middle age and is much more common in men than women.

Viral causes of acute laryngitis include:• Adenovirus infection • Influenza viruses• Measles virus• Mumps virus• Parainfluenza viruses• Respiratory syncytial virus• Rhinovirus infection (common cold virus)• Varicella zoster virus (chicken pox virus)

Croup• Croup (or laryngotracheobronchitis) is a respiratory

condition that is usually triggered by an acute viral infection of the upper airway.

• The infection leads to swelling inside the throat, which interferes with normal breathing and produces the classical symptoms of a "barking" cough and hoarseness. It may produce mild, moderate, or severe symptoms, which often worsen at night. Hospitalization is rarely required.

• Viral croup caused by parainfluenza virus, primarily types 1 and 2, in 75% of cases.

• Other viral etiologies include influenza A and B, measles, adenovirus and respiratory syncytial virus (RSV).

• Human parainfluenza viruses (HPIVs) are a group of four distinct serotypes of enveloped single-stranded RNA viruses belonging to the paramyxovirus family.

• They are the second most common cause of lower respiratory tract infection in younger children.

• Together, the parainfluenza viruses cause ~75% of the cases of Croup

• In immunosuppressed people, such as transplant patients, parainfluenza virus infections can cause severe pneumonia, which can be fatal.

2- Lower Respiratory Tract Viral Infections

Tracheitis• Tracheitis is most often caused by the bacteria Staphylococcus

auras. It frequently follows a recent viral upper respiratory infection.

• It affects mostly young children, possibly because their small trachea is easily blocked by swelling.

Symptoms:• Increasing deep or barking croup cough following a previous upper

respiratory infection• Crowing sound when inhaling (inspiratory stridor)• 'scratchy' feeling in the throat• Chest pain, Fever, Ear ache, Trouble breathing, Headache and

Dizziness (light headed) .

Bronchitis• Bronchitis is inflammation of the mucous membranes of the bronchi . It also can be divided into two categories, acute and chronic, each of which has unique etiologies, pathologies, and therapies.

Acute bronchitis is characterized by the development of a cough, with or without the production of sputum, mucus.

• It often occurs during the course of an acute viral illness such as the common cold or influenza.

• Viruses cause about 90% of cases of acute bronchitis, whereas bacteria account for less than 10%.

Chronic bronchitis, a type of chronic obstructive pulmonary disease, is characterized by the presence of a productive cough that lasts for three months or more per year for at least two years.

Bronchiolitis• Bronchiolitis is an acute inflammation of the

bronchioles (a common disease in infancy) usually caused by viruses.

• This is most commonly caused by respiratory syncytial virus. Other viruses include metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus.

Human metapneumovirus (hMPV) is a negative single-stranded RNA virus of the family Paramyxoviridae.

• It may be the second most common cause (after the respiratory syncytial virus) of lower respiratory infection in young children.

• Compared with respiratory syncytial virus, infection with human metapneumovirus tends to occur in slightly older children and to produce disease that is less severe.

• Co-infection with both viruses can occur, and is generally associated with worse disease.

Pneumonia• Pneumonia is an inflammatory condition of the

lung, especially the alveoli .• There are many causes, of which infection is the

most common, infecting agents can be bacteria, viruses, fungi, or parasites.

• Diagnostic tools include x-rays and examination of the sputum.

• Pneumonia is a common disease that occurs in all age groups. It is a leading cause of death among the young, the old, and the chronically ill.

• The prognosis depends on the type of pneumonia, the treatment, any complications, and the person's underlying health.

• Viral pneumonia have been found to account for between 18—28% of pneumonia.

• Viruses can also make the body more susceptible to bacterial infections; for which reason bacterial pneumonia may complicate viral pneumonia.

• It is commonly caused by viruses such as influenza virus, respiratory syncytial virus (RSV), adenovirus, and parainfluenza.

• Herpes simplex virus is a rare cause of pneumonia except in newborns.• People with weakened immune systems are also at risk of pneumonia

caused by cytomegalovirus (CMV).

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.

• Symptoms of influenza can start quite suddenly one to two days after infection. Usually the first symptoms are chills, but fever is also common early in the infection, with body temperatures ranging from 38-39 °C. Other symptoms may also include:

• 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 and bird flue, gastrointestinal symptoms such as diarrhea and abdominal pain.

(may be severe in children with influenza B).

• Although it is often confused with other influenza-like illnesses, especially the common cold in the early stages of the infection, but a flu can be identified by a high fever with a sudden onset and extreme fatigue.

• Influenza is a more severe disease than the common cold and is caused by a different type of virus.

• In occasional cases, even for healthy young adults, flu can cause either respiratory distress syndrome or pneumonia. And in general, in occasional cases, flu can cause either direct viral pneumonia and/or secondary bacterial pneumonia.

Types of influenza viruses

• Influenza viruses are RNA viruses that make up three of the five genera of the family Orthomyxoviridae:

• Influenzavirus A• Influenzavirus B• Influenzavirus C

Structure of the influenza virion. The hemagglutinin (HA) and neuraminidase (NA) proteins are shown on the surface of the particle.

There are 16 different H antigens (H1 to H16) and nine different N antigens (N1 to N9). So, in theory, 144 different combinations of these

proteins are possible.

Influenzavirus A• This genus has one species, influenza A virus. Wild aquatic birds are the natural hosts

for a large variety of influenza A.• It is 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 type of

two proteins on the surface of the viral envelope:

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 (Bird 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

Influenzavirus B• This genus has one species, influenza B virus. Influenza B almost

exclusively infects human and is less common than influenza A.• This type of influenza mutates at a rate 2–3 times slower than type A

and consequently is less genetically diverse, with only one influenza B serotype.

• As a result of this lack of antigenic diversity, a degree of immunity to influenza B is usually acquired at an early age. However, influenza B mutates enough that lasting immunity is not possible.

• This reduced rate of antigenic change, combined with its limited host range (inhibiting cross species antigenic shift), ensures that pandemics of influenza B do not occur.

Influenzavirus 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.