Influenza virus


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Influenza virus

Summer Micro


Bacterial structure and functions

Staphylococcus epidermidis

Staphylococcus aureus

Staphylococcus saprophyticus

Streptococcus viridans

Streptococcus pneumoniae

Streptococcus pyogenes (Group A Strep)

Streptococcus agalactiae (Group B Strep)


Clostridium perfringens

Clostridium botulinum (Botulism)

Clostridium difficile (Pseudomembranous colitis)

Clostridium tetani (Tetanus)

Bacillus cereus (Food poisoning)

Listeria monocytogenes

Corynebacterium diphtheriae (Diphtheria)

Bacillus anthracis (Anthrax)


Actinomyces israelii

Escherichia coli

Salmonella (non-typhoidal)

Salmonella typhi (typhoid fever)

Pseudomonas aeruginosa


Klebsiella pneumoniae


Proteus mirabilis

Yersinia enterocolitica

Legionella pneumophila (Legionnaires disease and Pontiac fever)

Serratia marcescens

Bacteroides fragilis

Yersinia pestis (Plague)

Vibrio cholerae (Cholera)

Helicobacter pylori

Campylobacter jejuni

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

Francisella tularensis (Tularemia)

Bordetella pertussis (Pertussis/Whooping cough)


Haemophilus influenzae

Haemophilus ducreyi (Chancroid)

Pasteurella multocida

Mycobacterium tuberculosis (Tuberculosis)

Mycobacterium leprae

Mycobacterium avium complex (NORD)

Mycoplasma pneumoniae

Chlamydia pneumoniae

Chlamydia trachomatis

Borrelia burgdorferi (Lyme disease)

Borrelia species (Relapsing fever)


Treponema pallidum (Syphilis)

Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species

Coxiella burnetii (Q fever)

Ehrlichia and Anaplasma

Gardnerella vaginalis (Bacterial vaginosis)

Viral structure and functions

Varicella zoster virus


Epstein-Barr virus (Infectious mononucleosis)

Human herpesvirus 8 (Kaposi sarcoma)

Herpes simplex virus

Human herpesvirus 6 (Roseola)


Parvovirus B19

Human papillomavirus

Poxvirus (Smallpox and Molluscum contagiosum)

BK virus (Hemorrhagic cystitis)

JC virus (Progressive multifocal leukoencephalopathy)




Hepatitis A and Hepatitis E virus

Hepatitis D virus

Influenza virus

Mumps virus

Measles virus

Respiratory syncytial virus

Human parainfluenza viruses

Dengue virus

Yellow fever virus

Zika virus

Hepatitis C virus

West Nile virus





Human T-lymphotropic virus

Ebola virus

Rabies virus

Rubella virus

Eastern and Western equine encephalitis virus

Lymphocytic choriomeningitis virus


Prions (Spongiform encephalopathy)


Influenza virus


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USMLE® Step 1 questions

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High Yield Notes

3 pages


Influenza virus

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USMLE® Step 1 style questions USMLE

of complete

A pharmaceutical scientist discovers a new drug that can inhibit the binding of the influenza virus to respiratory epithelial cells in subjects. Which of the following proteins is most likely being targeted with this drug?  

External References

First Aid



Haemophilus influenzae p. 138

influenza p. 165

Influenza p. 165

antigenic variation p. 106

orthomyxovirus p. 163

pneumonia p. 645

Reye syndrome and p. 373

treatment/prevention p. 197

vaccine for p. 107, 158

Staphylococcus aureus p. 131

influenza p. 165

Streptococcus pneumoniae p. 132

influenza p. 165


Content Reviewers

Rishi Desai, MD, MPH


Tanner Marshall, MS

Influenza, the virus that causes the flu, is one of the most common infectious diseases.

Now, there are three types of influenza that infect humans, called type A, type B, and type C, each one with slightly different genome and proteins.

Influenza belongs to the virus family Orthomyxoviridae - and type A and B have genomes that are made up of eight RNA segments, whereas type C, has a seven-segment RNA genome, with each segment containing a few genes.

Now, type A, the most common type of influenza virus, can be further subdivided based on two of the glycoproteins on its protective envelope surface; H protein, or Hemagglutinin, and N protein, or neuraminidase.

Hemagglutinin and Neuraminidase can vary a bit in their structure, so different versions are identified by a number.

For example, type A subtype H3N2, sometimes just called H3N2, has hemagglutinin number 3 and neuraminidase number 2 on its surface.

H3N2 and H1N1 are the most common type A subtypes to infect humans, but they both also infect various animals.

To give the full name of a virus, we use the type, the original host that it came from, the location where the virus was first identified, which is usually a city, the strain number, the year of origin, and—for type A influenza—the subtype named by the H and N glycoproteins.

For example, an H1N1 type A flu virus of duck origin from the province of Alberta, Canada, that is the 35th strain discovered in 1976 would be called A/duck/Alberta/35/76 (H1N1).

Type B influenza is less common, it only infects humans and doesn't mutate as often as type A.

Type B influenza only has a few types of H and N glycoproteins on its surface.

Therefore the naming pattern is similar to type A influenza without the H and N subtype included at the end or the host type, since it only infects humans.

For example, a type B virus found in Yamagata, Japan, which is the 16th strain discovered in 1988 would be called B/Yamagata/16/88.

Finally, there's type C influenza which is only one species, and is the least common and least likely to mutate of the three.

Influenza C usually causes mild disease in children, and unlike type B, it can affect both humans and pigs.


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