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Flashcards in Viral Respiratory Infections Deck (42):
1

mechanisms used by respiratory tract pathogens to initiate disease

sufficient number of virus inhaled or acquired by direct contact

infectious particles are often airborne

infectious virus must remain alive and viable during transmission

virus must be deposited on susceptible tissue in the host

2

general approaches to prevention/treatment of respiratoory infections

genetically engineered or selected vaccines

passive antibodies - humanized, pooled, or human monoclonals

drugs against virus specific proteins or enzymes

hand washing - avoiding close contact

supportive care

3

orthomyxovirus

influenza A, B, and C

A infects both humans and animals

B and C only infect humans

influenza A most important - associated with epidemics and pandemics

particles are highly pleiomorphic - mostly pspherical or ovoid

4

components of the influenza A virion

host derived lipid bilayer that includes hemagglutinin (HA) and neuraminidase (NA)

inner shell is composed of matrix protein (M1)

nucleocapsid contains viral genome with eight unique segments, all are required to be infectious

5

H antigen

hemagglutinin

required for binding the influenza virus to the host cell

6

N antigen

neuraminidase

helps the mature virus escape from the cell

7

Describe the replication cycle of influenza.

 Influenza binds to surface, endocytosed

Channel protein allows acidification of the vurlent particle

Release of genome into cell

Genome made in nucleus, transport into cytoplasm

Virus assembled and released

Two key steps - acidification step and the neuraminidase release step

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classification of influenza

three types of H antigen

two types of N antigen

different combinations make different viruses

9

antigenic drift

changes in the discrete highly variable domains of the viral proteins through random mutations

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antigenic shift

dramatic changes in virus by reassortment with another influenza virus

animals serve as a pool and where reassortment occurs due too infection with both animal and human viruses

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epidemic flue

cyclic and usually caused by type B or type A

type A occur every 2 to 3 years, and type B occurs every 4 to 6 years

overall mortality rate is 1%

12

route and spread of influenza infection

entry via respiratory tract through inhalation

viral infection and spread is normally lmited to the epithelial cells of the respiratory tract

13

influenza pathogenesis

infects primarily upper and lower respiratory tract

influx of macrophages and lymphocytes

spectrum of disease ranges from asymptomatic infection to primary viral pneumonia

release of IL1 triggers fiver

release of interferon triggers aches and pains

humoral response is important for the control of these infections

replication of the virus causes desquamationof the ciliated epithelium, hyperplasia of transitoral cells, and increased secretions

inbucation time is 1 to 3 days

14

prevention/treatment of influenza

vaccinate those who are at risk

vaccines made from reassortment of egg-adapted strains that are then formalin inactivated

15

M2 protein

influenza protein channel that allows acidification for uncoating of the virus

permits flow of ions from the endosome into the virion center to disrupt interactions and release the viral genome

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amantadine and rimantadine

drugs active against influenza A viruses

target is the M2 protein

prevents uncoating of the virus

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Relenza and Tamiflu (oseltamivir phosphate)

neuraminidase inhibitor

block the cleavage of sialic acid and prevent virus from budding out of the host cell and infecting other cells

relenza must be inhaled

18

syndromes potentially caused by influenza virus

uncomplicated rhinotracheitis

respiratory viral infection followed by bacterial pneumonia

viral pneumonia

usually rapid onset pneumonia

19

coronaviruses

~13 species in the family

infect not only humans but also cattle, pigs, rodents, cats, dogs, and birds

an example would be SARS

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coronavirus morphology

particles are irregulalry-shaped

~60-220nm in diameter

outer envelope bearing distinctive "club-shaped" proteins

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pathogenesis of coronaviruses

can cause respiratory infections, enteric infections, and neurologic syndromes

transmitted by aerosols of respiratory secretions

growth appears to be localize din the epithelium of URT

most infections cause a mild, self-limited disease

greatest incidence in children, less common in adults

reinfections appear to occur

immunization may be difficult

22

Severe Acute Respiratory Syndrome (SARS)

a respiratory illness caused by a coronavirus

civets and ferrets harbor this virus

symptoms include cough, shortness of breath, difficult breathing

severe virus capable of causing death

23

MERS virus

coronavirus that went from bats to humans through camels

24

paramyxovirus

family divided into three genera - paramyxovirus, pneumovirus, and morbillivirus

25

parainfluenzavirus 1-4

a type of paramyxovirus that causes an acute respiratory disease

can cause mild influenza-like illness as well as bronchitis, croup, and pneumonia

common infection of children

transmitted by aerosols, usually limited to URT

infections of LRT lead to more serious symptoms

little serological variation, rare in adults

26

pneumovirus

a genera of paramyxovirus that includes respiratory syncytial virus (RSV)

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morbillivirus

a genera of paramyxovirus that includes measles and canine distemper virus

28

mumps

humans are the only natural reservoir

transmission through saliva and respiratory secretions

typically causes painful swelling of parotid glands 16-18 days after infection

preceded by primary replication of the virus in epithelial cells of the URT and local lymph nodes

self-limited in children, but in adults a proportion of cases have other symptoms such as orchitis, meningitis, encephalitis, pancreatitis, myocarditis, nephritis

29

mumps prevention

one invariant serotype

vaccines are available

both formalin-inactivated and live attenuated exist

latter is widely used

30

measles

one of the most infectious diseases known

after a 10-12 day incubation period, dry cough, sore throat, conjunctivitis

rad rash and Koplik spots a few days later

complications include bronchopneumonia and otitis media and encephalitis

subacute schlerosing pan encephalitis results form a rare strain

31

prevention of measles

both live and killed vaccines exist

trivalent live attenuated vaccine (MMR) usually given

virus best avoided during pregnancy

32

RSV

major cause of LRT disease in infants and young children

highly infectious, transmission by respiratory secretions

primary multiplication occurs in epithelial cells of URT, producing a mild illness

in ~50% of children less than 8 months old, virus subsequently spreads into the LRT, causing bronchitis, pneumonia, and croup

currently no vaccine

infection does not result in lasting protection, so there can be repeated infections throghout life

33

treatment of RSV

ribavirin is used

effectiveness is not ensured

Respigram or Palivizumab are new drugs for prevention

34

picornaviruses

among the most diverse

genomic RNA is infectious

translates a large polyprotein

35

Coxackievirus

a subgroup of picornavirus

classified as an enterovirus

seasonal, epidemic pattern of infection

mostly sub-clinical

can be associated with meningitis, paralysis, and myocarditis

36

rhinovirus

a subgroup of the picornaviruses

~105 serotypes, repeated infections

optimum growth temperature of 33 degrees C, good for URT infection

symptoms due to damage to ciliated epithelium in URT

can predispose to secondary bacterial infections

no effective prophylaxis or treatment

little or no cross-protection between serotypes

37

adenovirus

frequent cause of acute URT infections

infections are common, most people have been infected by at least 1 type by age 15

commonly associated with a variety of clinical syndromes - little morbidity associated with infection

38

diseases associated with adenoviruses

acute respiratory illness

pharyngitis

gastro-enteritis

conjunctivitis

pneumonia

keratoconjunctivitis

acute hemorrhagic cystitis

hepatitis

39

adenovirus morphology

non-enveloped, 60-90nm in diameter

icosahedral symmetry

easily visible in the electron microscope by negative staining

thin glycoprotein fiber (IV) protrudes from the center of each penton

40

adenovirus prevention

no treatment options available

inactivated or attentuated vaccines have been developed

recent interest in gene therapy using adenoviruses for therapeutic purposes because the genome is easily manipulated in vitro

41

reovirus

produce minor upper respiratory tract infectiosn and gastrointestinal disease

42

hantavirus

infections caused by inhaling the virus contained in dried derr mouse (rodents) saliva, urine, or feces

may evolve into a fatal disease characterized by respiratory insufficiency

hantavirus pulmonary syndrome (HPS) characterized by an initial fever followed by the abrupt onset of acute pulmonary edema and shock