Viral infections of the upper respiratory tract

Question 1

Three most common causes of the common cold

Answer 1

1. rhinovirus 2. coronavirus 3. influenza virus

Question 2

Features of viral respiratory infections:

Answer 2

1. Virions reach respiratory tract by fomites (e.g. fingertips touch eyes) or aerosol transmission
2. Epi cells (conjunctiva, respiratory tract) are first site of virus-host interaction
3. Infected epi cells release cytokines that cause typical symptoms of viral disease: fevers, aches, etc.
4. Temp differential!! b/w upper and lower respiratory tract has consequences for pathogenesis: e.g. rhinoviruses replicate preferentially in URT (COLDER temps); it’s the differential basis for ATTENUATED virus vaccines
5. Age effect (infants and elderly with more severe respiratory infections)

Question 3

Acute infection is; persistent replication is; systemic replication is; examples of each

Answer 3

1. has replication confined to respiratory mucosal surface (picornavirus like rhinovirus, coronavirus, paramyxo with parainfluenza and RSV, orthomyxo with influenza)
2. on respiratory mucosal surface: EBV, adenovirus, papillomavirus
3. dissemination after primary replication in respiratory tract (pramyxo like mumps and measles, herpesviruses, rubella, picornavirus like polio)

Question 4

Coronaviruses facts:

Answer 4

1. negative ssRNA virus
2. think COLD-LIKE SYMPTOMS
3. rare new strains can cause lethal respiratory diseases (SARS and MERS with latter coming from fruit bats to camels to humans, going from ME to Europe)

Question 5

Myxoviruses like _____ and _____

Answer 5

bind to mucin protein on RBCs (ortho like influenza, para like measles)

Question 6

Differences b/w orthomyxo and paramyxo; similarity?

Answer 6

Nuclear replication and segmented negative ssRNA (8 segments) in orthomyxo; paramyxo with cytoplasmic replication and non-segmented negative ssRNA;

Question 7

How does influenza virus cause disease? Symptoms?

Answer 7

Mainly by combination of T cells responses (interleukins), interferon induction, and desquamation of mucus-secreting and ciliated cells (after aerosol inoculation of virus and replication in respiratory tract);
Fever, headache, tired, cough, sore throat, body aches, diarrhea and vomiting

Question 8

How to treat and prevent flu?

Answer 8

1. Antiviral drugs (oseltamivir and zanamivir for Flu A and B)
2. Vaccines: think of the trivalent inactivated vaccine (Fluzone) vs. live attenuated vaccine (FluMist0

Question 9

What is within the three genera of paramyxoviridae?

Answer 9

1. Pneumovirinae (RSV)
2. Morbillivirus (measles, canine distemper)
3. Paramyxovirinae (mumps, parainfluenza virus)

Question 10

Croup: which two viruses and some facts:

Answer 10

1. RSV and parainfluenza
2. peak incidence in winter
3. starts like a COLD in adults and infants
4. infants could have distinctive barking cough (CROUP)
5. Treat at home with steam and humidifiers
6. Comps include pneumonia and respiratory distress

Question 11

Adenovirus respiratory infections:

Answer 11

1. Icosahedral naked DNA virus
2. infects birds, mammals, humans
3. established cell lines from adenoidal tissue
4. Wide vareity: many people infected by at least 1 by age 15
5. Adenovirus infections very common and involve respiratory, GI tracts, or eye;
   think febrile upper tract infection or pharyngoconjunctival fever

Question 12

More facts on adenovirus disease, path, and epidemiology:

Answer 12

1. Aerosol, close contact (swimming pools), fecal-oral, fingers, ophthalmologic instruments as transmission
2. Virus infects mucoepithelial cells of respiratory and GI tract, conjunctiva, cornea
3. Virus persists in lymphoid tissue (tonsils, adenoids, Peyer’s)
4. Ab ESSENTIAL to recover;
5. No seasonal incidence
6. At risk: children under 14, day care centers, military camps, swimming clubs
7. Vaccine: Live attenuate; given to MILITARY PERSONNEL and helped with Ad4 infection incidence plummeting