Viruses

Question 1

Norovirus

Answer 1

Single stranded RNA
non-enveloped

Spread: faecal-oral, aerosol, contaminated water/food
Symptoms: GI, D&V

Question 2

Influenza virus

Answer 2

RNA virus
3 main types
Influenza A: mainly infects birds
Influenza B: mainly infects humans
Influenza C: mainly infects humans, dogs, pigs (less common)

spread: aerosol (coughs or sneezes), touching surfaces contaminated by the virus and then touching the mouth or eyes.

The infection may be confirmed by testing the throat, sputum, or nose for the virus. (PCR)

common symptoms: a high fever, runny nose, sore throat, muscle pains, headache, coughing, and feeling tired.
typically begin two days after exposure to the virus and most last less than a week. The cough, however, may last for more than two weeks

Complications: viral pneumonia, secondary bacterial pneumonia, sinus infections, and worsening of previous health problems such as asthma or heart failure.

Treatment: mainly treat symptoms (fluids, paracetamol for fever)

Prevention: hand washing, yearly vaccination

Question 3

Human Immunodeficiency Virus (HIV)

Answer 3

a lentivirus (a subgroup of retrovirus): single-stranded, positive-sense, enveloped RNA viruses
causes HIV infection and acquired immunodeficiency syndrome (AIDS): progressive failure of the immune system that allows life-threatening opportunistic infections and cancers to thrive.

Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk.

HIV infects vital cells in the human immune system such as helper T cells (specifically CD4+ T cells), macrophages, and dendritic cells.
leads to low levels of CD4+ T cells
When CD4+ T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.

Question 4

Hepatitis B

Answer 4

DNA
caused by the hepatitis B virus (HBV) which affects the liver.
Many people have no symptoms during the initial infection.
Some develop a rapid onset of sickness with vomiting, yellowish skin, feeling tired, dark urine and abdominal pain; Often these symptoms last a few weeks
It may take 30 to 180 days for symptoms to begin.
Most of those with chronic disease have no symptoms; however, cirrhosis and liver cancer may eventually develop.

transmitted by exposure to infectious blood or body fluids. Infection around the time of birth or from contact with other people’s blood during childhood is most common in areas where the disease is common.
In areas where the disease is rare, intravenous drug use and sexual intercourse are the most frequent routes of infection.

The infection can be diagnosed 30 to 60 days after exposure. Diagnosis is typically by testing the blood for parts of the virus and for antibodies against the virus.
It is one of five known hepatitis viruses: A, B, C, D, and E.

preventable by vaccination
In those who develop chronic disease antiviral medication such as tenofovir or interferon maybe useful, however these drugs are expensive.

Question 5

Varicella Zoster

Answer 5

one of eight herpes viruses
only affects humans
commonly causes chickenpox in children, teens and young adults and herpes zoster (shingles) in adults and rarely in children.

multiplies in the lungs, and causes a wide variety of symptoms. After the primary infection (chickenpox), the virus goes dormant in the nerves, including the cranial nerve ganglia, dorsal root ganglia, and autonomic ganglia. Many years after the patient has recovered from chickenpox, VZV can reactivate to cause a number of neurologic conditions.