Microbiology-Viral Meningitis

Question 1

What types are viruses are particularly prone to going viremic and causing meningitis?

Answer 1

Systemic paramyxoviruses (respiratory tract -> blood), enteroviruses (gains access through the mouth -> gut -> blood), arboviruses (direct injection into blood from arthropod).

Question 2

What are major viruses that gain access to neurons, spread to the brain and cause encephalitis?

Answer 2

Herpes virus and rabies virus

Question 3

What does neuronal viral spread typically lead to?

Answer 3

Encephalitis (neurons are being killed off)

Question 4

What does viremia typically lead to?

Answer 4

Meningitis

Question 5

What virus type is the most common cause of meningitis across all age groups?

Answer 5

Enteroviruses (85-95%)

Question 6

What acute CNS problems can happen in patients who are infected with measles and were never vaccinated?

Answer 6

Acute disseminated encephalomyelitis (ADEM)

Question 7

What slow progressing CNS problems can happen in people who are immunocompromised?

Answer 7

Measles inclusion body encephalitis (MIBE)

Question 8

What very slow progressing CNS problems can happen in people who had measles as a kid that don’t present until adulthood?

Answer 8

Subacute sclerosing panencephalitis (SSPE)

Question 9

How do you differentiate between viral meningitis and encephalitis?

Answer 9

Meningitis: nuchal rigidity & photophobia. Encephalitis: alterations in consciousness, seizures, paralysis and changes in vision or sensation.

Question 10

What agents of viral encephalitis are specialized neuron killers?

Answer 10

Herpes (hemorrhagic necrosis and neuronophagia), Poliovirus (motor neuron destruction) and Rabies virus

Question 11

How do you differentiate viral from bacterial meningitis?

Answer 11

Spinal tap and CSF analysis in the lab. You can also look for IgG antibodies in the CSF specific for the infecting agent.

Question 12

Why is poliovirus so infectious? What are its viral characteristics?

Answer 12

It is a picornavirus: non-enveloped, 5,3 and 2 fold axis of symmetry, isocahedral structure, +ssRNA (VERY INFECTIOUS) that will produce a long polyprotein precursor

Question 13

What enteroviruss cause meningitis and encephalitis?

Answer 13

Polio, coxsackie and echo viruses. These all have the brain and meninges as their target tissues.

Question 14

How many serotypes are there of poliovirus? What are the different polio vaccines?

Answer 14

3 serotypes. Salk = killed vaccine (all 3 serotypes). Sabin = oral attenuated vaccine (all 3 serotypes, increased amount of secretory IgA).

Question 15

How is poliovirus spread?

Answer 15

Fecal oral route, particularly in contaminated water

Question 16

What determines if poliovirus will cause paralysis or be eliminated without the host even knowing?

Answer 16

How quickly antibody can be made before viremia occurs and the virus gains access to the CNS

Question 17

Why are parents who have not been vaccinated against polio at risk for paralysis when their child has been given the Sabin vaccine?

Answer 17

Reversion: serotype three mutates fairly easily and can infect the immunodeficient parent while changing diapers.

Question 18

Why would Sabin be preferred to Salk when vaccinating kids against polio?

Answer 18

Sabin only requires one dose

Question 19

How can labs determine whether the poliovirus in a caretaker is related to the vaccine strain or is a wild-type virus?

Answer 19

Determine the nucleic acid sequence of the virus

Question 20

What arboviruses are associated with encephalitis? Where do these come from?

Answer 20

*

Question 21

What are the clinical symptoms of arbovirus infection?

Answer 21

Fever, rash, aches and chills. Progression to encephalitis is indicated by changes in mental status (seizures, optic neuritis, ataxia etc.)

Question 22

What is the main way to prevent arbovirus spread? What puts you at highest risk for severe CNS infection?

Answer 22

Vector control. Advanced age puts you at highest risk for severe infection.

Question 23

A 50 year old male comes to see you complaining of fever, rash, aches and chills. He also had a seizure this morning. He works at the zoo. What portion of the zoo is this patient most likely to work in if serology reveals West Nile Virus?

Answer 23

Birds

Question 24

A 50 year old male comes to see you complaining of fever, rash, aches and chills. He also had a seizure this morning. He works on a farm. What animals is he most likely to work with if he is diagnosed with Japanese encephalitis?

Answer 24

Pigs. Pigs have standing water that attracts mosquitos and then mosquitos give us the virus. Birds can also be a reservoir.

Question 25

What are the different types of Toga viruses? Which are more prevalent?

Answer 25

Western Equine Encephalitis (prevalent), Eastern EE (rare, but most fatal) and Venezuelan EE (prevalent and weaponized).

Question 26

What are the different types of Bunyaviruses? How are these spread?

Answer 26

California encephlitis, La Crosse. They are spread by the Aedes mosquito.

Question 27

What is the most important cause of pediatric arbovirus encephalitis in the US?

Answer 27

La Crosse

Question 28

What types of viral encephalitis peak during the summer?

Answer 28

Enteroviruses, tick-borne and mosquito-borne viruses

Question 29

A 21 year old man comes to see you in the ED with a sudden onset fever, headache, and severe low back pain. He just came back from SE Asia 3 days ago. Physical exam reveals a faint maculopapular rash and conjunctivitis. How was the causal virus most likely transmitted?

Answer 29

Insect (possible JE, Dengue or Chikungunya)

Question 30

What are the viral characteristics of the virus shown below?

Answer 30

This is a bullet-shaped rhabdovirus (possibly Rabies). -ssRNA, enveloped.

Question 31

What are risks for rabies in the US?

Answer 31

Animal saliva (raccoons, skunks), bat feces and organ donation from a previously infected host that never manifested symptoms.

Question 32

A patient comes to see you with a fever and headache that started yesterday. His throat hurts really bad and he is delirious. History reveals being bitten by a raccoon 19 years ago. Peripheral nerve biopsy is shown below. How will this virus progress through his nervous system if it goes untreated?

Answer 32

This patient has rabies, note the Negri cytoplasmic inclusion body. Rabies is taken up by peripheral nerves at the site of infection. It is transported via retrograde axoplasmic flow to the CNS if left untreated.

Question 33

A bunch of boys were out feeding a dog, but the dog wouldn’t eat any of their food and bit one of them and ran away. How would you want to treat these boys?

Answer 33

HRIG (passive human antibody) + vaccinate before symptoms begin and they will not develop rabies.

Question 34

What is a key clue for meningitis or encephalitis if you think a patient might have mumps?

Answer 34

Parotid gland swelling

Question 35

What paramyxoviruses can cause encephalitis or meningitis?

Answer 35

Measles and mumps

Question 36

What type of viral meningitis may present with a maculopapular rash? What do you know about the progression of this infection if you see this rash?

Answer 36

Measles. The skin is the last of all the organs to get infected, so you know everything else has been hit by measles.

Question 37

What physical exam finding will you see in measles just prior to skin manifestations?

Answer 37

Koplik’s spots on the inside of the cheeks.

Question 38

How might you see herpes virus infection on CT or MR?

Answer 38

HSV encephalitis will show decreased density and loss of sulci

Question 39

What viruses can cause congenital viral meningitis? What would you look for on CT scan of a pregnant woman with possible CMV encephalitis?

Answer 39

HSV-2 (during delivery) and CMV (most frequent cause of congenital viral infection). With CMV you may see CNS calcifications.

Question 40

What drugs do you give to a pregnant woman with herpes to prevent microcephaly in the neonate? How do these drugs work?

Answer 40

Acyclovir or Ganciclovir. They work by causing early chain termination during viral replication.

Question 41

What types of viral encephalitis are patients with HIV at particular risk for?

Answer 41

PML (progressive multifocal leukoencephalopathy) which causes widespread demyelination.

Question 42

A 75 year old woman presents with a fever, focal seizures and muscular weakness on one side of her body. MRI reveals hemorrhagic lesions in the inferior medial portion of her temporal lobe. What antiviral treatment is recommended?

Answer 42

Acyclovir is used to treat this possible herpes infection.