Viruses in public health

Question 1

Name some of the main viruses linked to human cancer.

Answer 1

Human papillomavirus (HPV), Epstein-Barr Virus (EBV), Hepatitis C and B Virus (HCV and HBV).

Question 2

In what way may viruses cause cancer in human?

Answer 2

Most viral genomes encode proto-oncogenes. This is a potential cause of cancer.

Question 3

What is the name of the virus causing smallpox?

Answer 3

Variola virus.

Question 4

How is smallpox transmitted?

Answer 4

Trough contact and/or respiratory droplets.

Question 5

What is the current incidence of smallpox?

Answer 5

0. (It was eradicated solely due to vaccination.)

Question 6

What made smallpox a good candidate for eradication?

Answer 6

No animal reservoir.
No asymptomatic infection.
No latent infection.
No chronic infection.
Little genetic variety.
Slow spread.

Question 7

How does poliomyelitis spread?

Answer 7

Through fecal-oral transmission.

Question 8

What types of vaccines are available for poliomyelitis?

Answer 8

Viable-attenuated oral vaccine and injected inactivated vaccine.

Question 9

What is the cause of death due to poliomyelitis?

Answer 9

Respiratory paralysis.

Question 10

What is acute flaccid paralysis?

Answer 10

An abnormal condition related to weakened muscles or loss of muscle tone.

Question 11

What makes polio a candidate for eradication? Are there any reasons polio isn’t a good candidate for eradication?

Answer 11

The fact that there is no animal reservoir or latent infection and an effective (and safe) vaccine makes polio a good candidate for eradication.

However, polio has a chronic and sometimes asymptomatic infection, high genetic variability and quick spread.

Question 12

In which two countries is polio endemic?

Answer 12

Afghanistan and Pakistan.

Question 13

How many types of wild polio is there, and which of the types is the most virulent?

Answer 13

There are three wild types of polio: Poliovirus 1, 2 and 3.

Poliovirus 1 is the most virulent and is the cause of 90 % of poliomyelitis.

Question 14

What is one of the main obstacles preventing us from eradicating poliomyelitis?

Answer 14

Vaccine derived polio is a problem.

(In the oral viable polio vaccine only a handful of mutations separate the vaccine from wild polio. Everyone who gets the oral vaccine sheds virulent revertant and recombinant viruses. These viruses can circulate in the population and cause poliomyelitis in unvaccinated individuals.)

Question 15

How is measles spread?

Answer 15

Through airborne transmission.

Question 16

What are potential complication from measles?

Answer 16

Blindness, encephalitis, diarrhea and pneumonia.

Question 17

What puts children in highest risk of death owing to measles?

Answer 17

Malnutrition.

Question 18

How is measles prevented/treated?

Answer 18

Measles can be prevented with a viable-attenuated vaccine.

Treatment is supporting, e.g. re-hydration. Giving vitamin A is also part of treatment.

Question 19

How is Rubella spread?

Answer 19

Through respiratory droplets or contact.

Question 20

What are the major complications from Rubella?

Answer 20

The major complication occur due to maternal infections during pregnancy and include miscarriage and congenital rubella syndrome (CRS).

Question 21

What is the classic triade for congenital rubella syndrome?

Answer 21

Cataract.
Heart anomalies.
Deafness.

Question 22

To provide heard immunization a certain percentage if the population has to be vaccinated. What determines this percentage?

Answer 22

The reproduction number (R0) and vaccine efficacy.

Question 23

What is reproduction number (R0)?

Answer 23

The number of people a single infected individual transmits the infection to.

Question 24

How is HIV transmitted?

Answer 24

Through blood or sexual contact.

Question 25

What is the name of the disease caused by human immunodeficiency virus (HIV)?

Answer 25

Acquired immunodeficiency syndrome (AIDS).

Question 26

What types of vaccines are available for HIV?

Answer 26

None.

Question 27

How is HIV treated?

Answer 27

The infection is not curable, but is treated with combination antiretroviral therapy (cART).

Question 28

How is PCR and serology used to diagnose/monitor HIV infected patients?

Answer 28

Serology is used to set the diagnosis.

PCR is used to asses viral load during treatment.

Question 29

Only one patient is fully believed to have been cured of HIV. Five more patient are possibly cured (but the evidence for this is not yet published.) What is the common denominator for all these patients?

Answer 29

Graft-versus-host disease.

Question 30

What is meant by antigen shift?

Answer 30

Antigenic shift is an abrupt, major change in an virus, resulting in new HA (hemagglutinin) and/or new HA and NA (neuraminidase) proteins in influenza viruses that infect humans. Shift can result in a new virus subtype in humans. One way shift can happen is when an virus from an animal population gains the ability to infect humans.

Antigens shift happen less frequently than antigen drifts and may cause a pandemic influenza.

Question 31

What is meant by antigen drift?

Answer 31

Antigen drift are small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus: HA (hemagglutinin) and NA (neuraminidase).

Antigen drift happens continually as the virus replicates and is often the cause of seasonal influenza.

Question 32

What is the clinician’s role in infectious disease consultation?

Answer 32

Take vaccination history and travel history.
Have knowledge on likely diagnoses.
Take samples for confirmation.
Treat - rational use of antivirals. 
Isolate.
Track records.
Report - MSIS.

Question 33

Explain what is meant by the following statement: “Measles vaccination preserves immunity to other pathogens”.

Answer 33

Measles infections in unvaccinated individuals wipe out immune memories of other pathogens, putting them at risk of other deadly diseases. The measles vaccine prevents this from happening.