284,770views

test

00:00 / 00:00

Influenza virus

Watch later

Watch later

Human herpesvirus 8 (Kaposi sarcoma)
Herpes simplex virus
Human herpesvirus 6 (Roseola)
Adenovirus
Parvovirus B19
Human papillomavirus
BK virus (Hemorrhagic cystitis)
JC virus (Progressive multifocal leukoencephalopathy)
Poliovirus
Coxsackievirus
Rhinovirus
Hepatitis A and Hepatitis E virus
Influenza virus
Mumps virus
Measles virus
Respiratory syncytial virus
Human parainfluenza viruses
Yellow fever virus
Zika virus
Hepatitis C virus
West Nile virus
Norovirus
Rotavirus
HIV (AIDS)
Rabies virus
Rubella virus
Prions (Spongiform encephalopathy)
Candida
Plasmodium species (Malaria)
Trypanosoma cruzi (Chagas disease)
Protein synthesis inhibitors: Aminoglycosides
Antimetabolites: Sulfonamides and trimethoprim
Antituberculosis medications
Miscellaneous cell wall synthesis inhibitors
Protein synthesis inhibitors: Tetracyclines
Cell wall synthesis inhibitors: Penicillins
Miscellaneous protein synthesis inhibitors
Cell wall synthesis inhibitors: Cephalosporins
DNA synthesis inhibitors: Metronidazole
DNA synthesis inhibitors: Fluoroquinolones
Mechanisms of antibiotic resistance
Integrase and entry inhibitors
Nucleoside reverse transcriptase inhibitors (NRTIs)
Protease inhibitors
Hepatitis medications
Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
Neuraminidase inhibitors
Herpesvirus medications
Azoles
Echinocandins
Miscellaneous antifungal medications
Anthelmintic medications
Antimalarials
Anti-mite and louse medications
Nuclear structure
DNA structure
Transcription of DNA
Translation of mRNA
Gene regulation
Epigenetics
Amino acids and protein folding
Nucleotide metabolism
DNA replication
Lac operon
DNA damage and repair
Cell cycle
Mitosis and meiosis
DNA mutations
Lesch-Nyhan syndrome
Adenosine deaminase deficiency
Purine and pyrimidine synthesis and metabolism disorders: Pathology review
Polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR)
Gel electrophoresis and genetic testing
ELISA (Enzyme-linked immunosorbent assay)
Karyotyping
DNA cloning
Fluorescence in situ hybridization
Mendelian genetics and punnett squares
Hardy-Weinberg equilibrium
Inheritance patterns
Independent assortment of genes and linkage
Evolution and natural selection
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fragile X syndrome
Huntington disease
Myotonic dystrophy
Friedreich ataxia
Turner syndrome
Klinefelter syndrome
Prader-Willi syndrome
Angelman syndrome
Cri du chat syndrome
Williams syndrome
Alagille syndrome (NORD)
Achondroplasia
Polycystic kidney disease
Familial adenomatous polyposis
Familial hypercholesterolemia
Marfan syndrome
Multiple endocrine neoplasia
Neurofibromatosis
Tuberous sclerosis
von Hippel-Lindau disease
Albinism
Cystic fibrosis
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Hemochromatosis
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Leukodystrophy
Niemann-Pick disease types A and B (NORD)
Niemann-Pick disease type C
Phenylketonuria (NORD)
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Alpha-thalassemia
Beta-thalassemia
Wilson disease
Alport syndrome
X-linked agammaglobulinemia
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hemophilia
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Muscular dystrophy
Wiskott-Aldrich syndrome
Mitochondrial myopathy
Autosomal trisomies: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
Miscellaneous genetic disorders: Pathology review
Human development days 1-4
Human development days 4-7
Human development week 2
Human development week 3
Ectoderm
Mesoderm
Endoderm
Development of the placenta
Development of the fetal membranes
Development of twins
Hedgehog signaling pathway
Development of the digestive system and body cavities
Development of the umbilical cord
Development of the cardiovascular system
Fetal circulation
Development of the face and palate
Pharyngeal arches, pouches, and clefts
Development of the gastrointestinal system
Development of the teeth
Development of the tongue
Development of the axial skeleton
Development of the muscular system
Development of the renal system
Development of the reproductive system
Development of the respiratory system
Cellular structure and function
Cell membrane
Selective permeability of the cell membrane
Extracellular matrix
Cell-cell junctions
Endocytosis and exocytosis
Osmosis
Resting membrane potential
Nernst equation
Cytoskeleton and intracellular motility
Cell signaling pathways
Adrenoleukodystrophy (NORD)
Zellweger spectrum disorders (NORD)
Ehlers-Danlos syndrome
Peroxisomal disorders: Pathology review
Introduction to biostatistics
Types of data
Probability
Mean, median, and mode
Range, variance, and standard deviation
Standard error of the mean (Central limit theorem)
Normal distribution and z-scores
Paired t-test
Two-sample t-test
Hypothesis testing: One-tailed and two-tailed tests
One-way ANOVA
Two-way ANOVA
Repeated measures ANOVA
Correlation
Methods of regression analysis
Linear regression
Logistic regression
Type I and type II errors
Sensitivity and specificity
Positive and negative predictive value
Test precision and accuracy
Incidence and prevalence
Relative and absolute risk
Odds ratio
Mortality rates and case-fatality
DALY and QALY
Direct standardization
Indirect standardization
Study designs
Ecologic study
Cross sectional study
Case-control study
Cohort study
Randomized control trial
Clinical trials
Sample size
Disease causality
Selection bias
Information bias
Confounding
Interaction
Prevention
Major depressive disorder
Suicide
Bipolar and related disorders
Major depressive disorder with seasonal pattern
Generalized anxiety disorder
Social anxiety disorder
Panic disorder
Phobias
Obsessive-compulsive disorder
Body focused repetitive disorders
Post-traumatic stress disorder
Schizophrenia
Delirium
Amnesia
Dissociative disorders
Anorexia nervosa
Bulimia nervosa
Cluster A personality disorders
Cluster B personality disorders
Cluster C personality disorders
Somatic symptom disorder
Factitious disorder
Tobacco dependence
Opioid dependence
Cannabis dependence
Cocaine dependence
Alcohol use disorder
Bruxism
Insomnia
Narcolepsy (NORD)
Erectile dysfunction
Attention deficit hyperactivity disorder
Disruptive, impulse control, and conduct disorders
Learning disability
Fetal alcohol syndrome
Tourette syndrome
Autism spectrum disorder
Rett syndrome
Mood disorders: Pathology review
Amnesia, dissociative disorders and delirium: Pathology review
Personality disorders: Pathology review
Eating disorders: Pathology review
Psychological sleep disorders: Pathology review
Psychiatric emergencies: Pathology review
Drug misuse, intoxication and withdrawal: Hallucinogens: Pathology review
Malingering, factitious disorders and somatoform disorders: Pathology review
Trauma- and stress-related disorders: Pathology review
Selective serotonin reuptake inhibitors
Serotonin and norepinephrine reuptake inhibitors
Tricyclic antidepressants
Monoamine oxidase inhibitors
Atypical antidepressants
Typical antipsychotics
Atypical antipsychotics
Lithium
Nonbenzodiazepine anticonvulsants
Anticonvulsants and anxiolytics: Barbiturates
Anticonvulsants and anxiolytics: Benzodiazepines
Psychomotor stimulants

Assessments

Flashcards

0 / 14 complete

USMLE® Step 1 questions

0 / 5 complete

High Yield Notes

3 pages

Flashcards

Influenza virus

0 of 14 complete

Questions

USMLE® Step 1 style questions USMLE

0 of 5 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?  

Transcript

Watch video only

Content Reviewers

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.

Rather than hemagglutinin and neuraminidase, type C influenza uses a hemagglutinin-esterase-fusion protein to enter and exit cells.

So, type C influenza is named without the HN subtype, similar to how type B's written.

For example, a type C virus found in Sao Paulo, Brazil which is the 37th strain discovered in 1982 would be called C/Sao Paulo/37/82.

Of the three types, type A is the most common and causes the most severe illness.

One reason is that the virus has a tendency to mutate its H and N glycoproteins during replication, and this allows daughter viruses to form that are slightly different from one another and from the parent virus.

Over time, if enough of these small changes happen, even if somebody's immune to the original virus, the mutated virus may have H and N glycoproteins that are different enough to allow it to evade antibodies, and therefore infect people who were immune to previous strains.

This process is called genetic drift, and is why individuals can get sick from influenza year after year or from two different strains of influenza in the same year.

In addition, a process called antigenic shift, is where sometimes a virus will be circulating among animal populations like pigs or chickens and then will suddenly change in a way that allows the virus to infect humans as well.

This happens when the same cell, let's say a pig cell, gets infected with two similar flu viruses, for example a flu strain that usually infects humans and one that usually infects pigs.

Since the viral genome is in segments of RNA, the pieces might reassort, or mix, allowing new viruses to have a mix of RNA segments in them.

Reassortment results in viruses that have entirely new hemagglutinin, neuraminidase, or both.

When a virus is produced that can infect human cells and has entirely new proteins, people have little or no protection against it, and it can rapidly spread through the population.

This antigenic shift process is responsible for three major influenza pandemics in the 20th century, including the Spanish Flu in 1918, which killed 3 percent of the world's entire population at the time.

The flu is transmitted when an infected person sneezes or coughs, which spreads thousands of droplets containing the virus into the local area, up to about two meters or six feet away.

These droplets can then land in the mouths or noses of people nearby, or get inhaled into the lungs.

The virus can also survive on surfaces for a few hours, so it's possible to get the virus by touching a surface, like a contaminated doorknob, and then touching your own eyes, nose, or mouth.

When the flu virus enters the body, it uses hemagglutinin to bind to sialic acid sugars on the surface of epithelial cells in the upper respiratory tract.

Once bound, the cell swallows up the virus in a process called endocytosis.

That viral RNA is negative-sense, meaning that each piece first has to be transcribed by RNA polymerase into positive-sense mRNA strands, before it can be translated into proteins and assembled into viruses.

These viruses leave the cell by simply budding out from it by using the neuraminidase, which cleaves the sialic acid sugars in the membrane, releasing the newly created viruses from the cell.

Influenza symptoms start 1-4 days after infection and include fever, headache, runny nose, sore throat, and a cough.

Most of these symptoms get better in a week, but the cough often persists for up to two weeks.

There can sometimes be complications, though, like acute otitis media, bronchiolitis, croup, sinusitis, and pneumonia, including antibiotic-resistant strains caused by Staphylococcus aureus and Streptococcus pneumoniae.

The highest risk of complications is among high-risk groups like young children under 6 months of age, pregnant women, adults over 65 years old, and those with chronic medical conditions, like chronic heart or lung disease.