RNA viruses – Part I

Poliovirus.

Infects the anterior horns of the spinal cord and causes polio myelitis (inflammation of spinal cord).

Classically causes degeneration of motor neurons in one leg, leading to one leg much smaller than the other leg.

Rotavirus.

Most common cause of watery diarrhea in unvaccinated children < 5 years. Immigrant status (e.g., from China) often implies unvaccinated status on USMLE.

Vaccine normally given orally at 2, 4, and 6 months of age.

Double-stranded, segmented RNA (NBME asks it). Wheel-shaped (also on NBME).

Coxsackie B virus.

Can cause pleurodynia, which is intercostal muscle spasm presenting with sharp, lateral chest pain, sometimes with an increase in serum CK due to the muscle spasm. Despite its name, it has nothing to do with the lungs and is an MSK condition. It shows up twice on the NBME content for 2CK. For Step 1, I’d still know what it is.

Causes myocarditis with dilated cardiomyopathy.

Can cause diabetes mellitus type I in susceptible patients. The immune system develops antibodies against a viral oligopeptide that cross-reacts with intra-beta-islet cell glutamic acid decarboxylase-65. Hence this one of the reasons why anti-GAD-65 antibodies are positive in some patients with type I DM.

IgM against HepA means acute infection.

IgG against HepA means patient has cleared infection (because there is no chronic HepA).

Coxsackie B virus.

Causes myocarditis with dilated cardiomyopathy.

Can cause diabetes mellitus type I in susceptible patients. The immune system develops antibodies against a viral oligopeptide that cross-reacts with intra-beta-islet cell glutamic acid decarboxylase-65. Hence this one of the reasons why anti-GAD-65 antibodies are positive in some patients with type I DM.

Can cause pleurodynia, which is intercostal muscle spasm presenting with sharp, lateral chest pain, sometimes with an increase in serum CK due to the muscle spasm. Despite its name, it has nothing to do with the lungs and is an MSK condition. It shows up twice on the NBME content for 2CK. For Step 1, I’d still know what it is.

Echovirus.

Coxsackie B virus.

Can cause diabetes mellitus type I in susceptible patients. The immune system develops antibodies against a viral oligopeptide that cross-reacts with intra-beta-islet cell glutamic acid decarboxylase-65. Hence this one of the reasons why anti-GAD-65 antibodies are positive in some patients with type I DM.

Causes myocarditis with dilated cardiomyopathy.

Can cause pleurodynia, which is intercostal muscle spasm presenting with sharp, lateral chest pain, sometimes with an increase in serum CK due to the muscle spasm. Despite its name, it has nothing to do with the lungs and is an MSK condition. It shows up twice on the NBME content for 2CK. For Step 1, I’d still know what it is.

Infects the anterior horns of the spinal cord and causes polio myelitis (inflammation of spinal cord).

Classically causes degeneration of motor neurons in one leg, leading to one leg much smaller than the other leg.

HepA is the answer for acute hepatitis in the United States most of the time. The Q might say the patient had recent travel to Mexico.

HepE notably causes fulminant hepatitis / ­­ high risk of death in pregnant women. It also is seen more in Asia, e.g., Tibet. But if USMLE says Mexico + pregnant woman + fast death from hepatitis, you still have to use your head and know that’s HepE over HepA.

Most common cause of watery diarrhea in adults and rotavirus-vaccinated children.

Cruise ships and business conferences are buzzy places to acquire (fecal-oral); basically any place with high density of people.

If the Q says a young child + family all have watery diarrhea, the answer is Norwalk, not Rota, since only the young child would get Rota, not the family also.

Norovirus (Norwalk virus).

Most common cause of watery diarrhea in adults and rotavirus-vaccinated children.

Cruise ships and business conferences are buzzy places to acquire (fecal-oral); basically any place with high density of people.

If the Q says a young child + family all have watery diarrhea, the answer is Norwalk, not Rota, since only the young child would get Rota, not the family also.

Rotavirus.

Most common cause of watery diarrhea in unvaccinated children < 5 years. Immigrant status (e.g., from China) often implies unvaccinated status on USMLE.

Vaccine normally given orally at 2, 4, and 6 months of age.

Double-stranded, segmented RNA (NBME asks it). Wheel-shaped (also asked on NBME).

Causes hand-foot-mouth disease, which presents as vesicles on – you’d never guess it – the hands, feet, and mouth. Almost always a pediatric condition, but adults can sometimes get it as well.

Can also cause herpangina, which is oropharyngeal vesicles.

Common cause of aseptic (viral) meningitis.

CSF analysis for viral meningitis is: normal protein; normal glucose; elevated lymphocytes.

Rhinovirus

USMLE wants you to know HepA vaccine is indicated for MSM and IV drug users. The latter in particular sounds weird, since HepA isn’t parenteral, but it’s asked. There’s a 2CK NBME Q where they just mention otherwise healthy MSM, and answer is Hep A vaccination. Students are confused, but I don’t know what to tell you.

Causes myocarditis with dilated cardiomyopathy.

Can cause diabetes mellitus type I in susceptible patients. The immune system develops antibodies against a viral oligopeptide that cross-reacts with intra-beta-islet cell glutamic acid decarboxylase-65. Hence this one of the reasons why anti-GAD-65 antibodies are positive in some patients with type I DM.

Can cause pleurodynia, which is intercostal muscle spasm presenting with sharp, lateral chest pain, sometimes with an increase in serum CK due to the muscle spasm. Despite its name, it has nothing to do with the lungs and is an MSK condition. It shows up twice on the NBME content for 2CK. For Step 1, I’d still know what it is.

Causes hand-foot-mouth disease, which presents as vesicles on – you’d never guess it – the hands, feet, and mouth. Almost always a pediatric condition, but adults can sometimes get it as well.

Can also cause herpangina, which is oropharyngeal vesicles.

Coxsackie A virus.

Causes hand-foot-mouth disease, which presents as vesicles on – you’d never guess it – the hands, feet, and mouth. Almost always a pediatric condition, but adults can sometimes get it as well.

Can also cause herpangina, which is oropharyngeal vesicles.

Causes Colorado tick fever, which is a flu-like illness. Mostly occurs in Western USA.

Salk vaccine = killed intramuscular.

Sabin vaccine = live-attenuated oral.

Only the live-attenuated vaccine is capable of generating a CD8+ T-cell response and IgA secretion in the gut.

This is because only live virus can invade the cell, leading to expression on MHC-I (which interacts with CD8). This occurs within the gut, since the vaccine is oral, so the Peyer’s matches in the ileum can be stimulated to make gut IgA.

The killed intramuscular vaccine can’t produce a CD8+ T cell response because killed virus can’t invade the cell. And since it doesn’t have exposure to the gut, there won’t be gut IgA produced.

USMLE will ask what is a common feature of these vaccines that accounts for their efficacy –> answer = “neutralizing antibodies in the circulation.” Both the killed and oral are capable of generating IgG antibodies in the circulation.

In short: only Sabin does CD8+ response and gut IgA production; both Salk and Sabin produce IgG in circulation.

If you’re confused about the immuno, I talk about this stuff in my HY Immuno PDF.

Most common cause of common cold (i.e., upper respiratory tract infection, with coryza, dry cough, no exudates, and no fever).

Nothing else you need to know.

Double-stranded, segmented RNA (NBME asks it). Wheel-shaped (also on NBME). Above and beyond other viral structures, the one for rotavirus is higher yield.

Most common cause of watery diarrhea in unvaccinated children < 5 years. Immigrant status (e.g., from China) often implies unvaccinated status on USMLE.

Vaccine normally given orally at 2, 4, and 6 months of age.