P2: V. MEDICALLY IMPORTANT RNA VIRUSES

• Includes the Rift Valley fever virus.

• The disease is common among domestic animals, such as cattle, buffalo, sheep, goats, and camels.

• The disease is primarily found in Africa.

• Recently, outbreaks were reported in Saudi Arabia and Yemen.

Phenuiviridae

• The virus is transmitted among hosts by mosquitoes.

• In humans, most infections are asymptomatic or produce a mild illness associated with fever and liver abnormalities.

• Patients with symptoms often experience fever, generalized weakness, back pain, and dizziness.

• A small percentage of those infected progress to more serious infection that can include ocular disease, encephalitis, or hemorrhagic fever.

Phenuiviridae

• Laboratory diagnosis is usually made by detecting antibodies in the serum or CSF.

• During the acute stage, virus can be detected by PCR or virus isolation in the CSF

Arenaviridae

• Most infected people are asymptomatic, but symptoms can range from mild to severe and life threatening.

• Rats are reservoirs and infection is acquired by contact with these animals.

• The disease is relatively common in West Africa

Arenaviridae

• Also a member of the Arenaviridae family.

• It generally causes asymptomatic or mild infection, although neurologic symptoms are present in some individuals.

• The mortality rate is less than 1%.

• Mice are reservoirs, and it is estimated that 5% of house mice in the United States carry it

lymphocytic choriomeningitis virus (LCMV)

• Are found worldwide, and rodents are important reservoirs.

• Contact with rodent feces, urine, or saliva can lead to human infections.

Hantavirus in humans can cause severe, life-threatening infections referred to as ______ and ______

hantavirus pulmonary syndrome (HPS) ; hemorrhagic fever with renal syndrome.

• Have a bullet-shaped, enveloped capsid ranging in size from 150 to 350 nm.

Rhabdovirus

It gains entry into humans by animal (e.g., cat, dog, or raccoon) bites, as well as contact with bats.

Rabies Virus

Rabies virus

• The virus first infects the ______ but preferentially infects ____

• The virus migrates along the _____ to the CNS.

• The disease progresses to produce convulsions, coma, and ____

• muscle tissue ; neurons.

• peripheral nerves

• fatal encephalitis

In rabies virus

• Post-exposure treatment is effective if administered within _____.

• Without rapid treatment, the infection is essentially 100% fatal.

• 72 hours

• Virions range in size from 800 to 1000 nm.

• Antigen capture by ELISA, RT-PCR, and detection of IgM antibodies can

  diagnose the infection a few days after onset of symptoms

• Bats are thought to be the reservoir, but the mode of transmission is unclear.

• Produces hemorrhagic fever with high fatality rates.

• Most cases occur in Africa.

Filoviridae

Filoviridae

• The family Filoviridae includes the ____ and _____ viruses

• Infection by these viruses produces  _____ with high fatality rates.

• Marburg and Ebola

• hemorrhagic fever

• Contains RNA, and the naked virion has an icosahedral shape.

• Ranges in size from 24 to 30 nm.

Hepatitis A Virus (HAV)

Hepatitis A Virus (HAV)

• It is a member of the family _____ and the genus ____

• Picornaviridae ; Hepatovirus

Infections

• Infections are spread by the fecal-oral route and are generally due to poor sanitation and hygiene. Food handling transmission is common.

• Humans can also acquire the infection from contaminated shellfish, including shrimp, oysters, scallops, etc.

• Vaccines are available.

Hepatitis A Virus (HAV)

Clinical characteristics

a. The incubation period is 15–40 days.

b. Liver involvement (jaundice), nausea, anorexia, and malaise

c. Mortality rate is less than 1%

Hepatitis A Virus (HAV)

Diagnosis

a. Clinical symptoms and liver enzymes, particularly alanine aminotransferase, are elevated.

b. Serology

Hepatitis A Virus (HAV)

Serologic indicators

• Anti-HAV IgM is positive in ______.

b. Anti-HAV IgG (positive) and anti-HAV IgM (negative) indicate a ____

c. General serology testing also includes ruling out hepatitis B and C viruses.

• acute infections

• past HAV infection.

• Contains partially double-stranded DNA.

• The complete virion has an envelope, ranges in size between 42 and 47 nm, and is sometimes referred to as Dane particles.

• The virus is unusual in that an RNA intermediate is required for replication of the genome.

• The virus needs a viral-encoded reverse transcriptase for eplication.

Hepatitis B Virus (HBV)

Hepatitis B Virus (HBV) is the member of the family

Hepadnaviridae

Infections

a. Infections are spread by contaminated body fluids, including blood. It can

be sexually transmitted.

b. Infections are associated with contaminated blood products, needle sticks,

tattoos, body piercing, intravenous drug abuse, and hemodialysis

Hepatitis B Virus (HBV)

a. The incubation period is 50–180 days.

b. Acute infections produce symptoms resembling HAV infections.

c. Chronic infections are common and can result in cirrhosis and hepatocellular carcinoma

Hepatitis B Virus (HBV)

Diagnosis

a. Clinical symptoms and elevated liver enzymes

b. Serology

Hepatitis B Virus (HBV)

Hepatitis B Virus (HBV)

• _____ is the first marker to be detected, but it will become negative as the patient produces antibody to HBsAg and recovers.

• ______ is positive in acute and chronic stages of infection. Presence of this

  marker also indicates that the patient is infectious

• ______ indicates recovery or immunity after HBV vaccination. The antibody is generally present for life

• Antibody to _____ is positive in acute infection stages. It indicates current or

  past infections but does not indicate recovery or immunity

• HBsAg

• HBeAg

• Antibody to HBsAg (anti-HBs)

• HBcAg

Hepatitis B Virus (HBV)

• _______ indicates acute infection.

• As anti-HBs is forming, the level of HBsAg is decreasing.

• During this transition, there is a point when both markers are undetectable.

• At this time, the only indicator of HBV infection is ____; this time period is called the “core window.”

• IgM antibody to HB core antigen (anti-HBc IgM)

• anti-HBc IgM

• Contains RNA, and the naked viruses range in size from 35 to 37 nm.

• Also called the delta virus.

• Requires but does not encode for HBsAg; therefore, it only replicates in cells also infected with HBV.

• Because of this dependency on HBV, it is sometimes referred to as a subvirus.

Hepatitis D Virus (HDV)

Hepatitis D Virus (HDV)

• ____ occurs when an individual acquires both HDV and HBV at the same time.

• A ___ is when a patient with an HBV infection is exposed to HDV.

• Superinfections are more severe than coinfections.

• Coinfection

• superinfection

Diagnosis

a. Detection of anti-HDV and HDV RNA

b. Serologic markers for HBV will also be positive; in particular, HBsAg.

Hepatitis D Virus (HDV)

contains RNA and has a lipid envelope

Hepatitis C Virus (HCV

Hepatitis C Virus (HCV)

• The virus is a member of the family _____ and the genus ____.

• Flaviviridae ; Hepacivirus

Infections

• A common cause of hepatitis worldwide and the primary factor requiring a liver transplant.

• Spread through contaminated blood products, organ transplants, hemodialysis, and intravenous drug abuse

• No vaccine currently exist

Hepatitis C Virus (HCV)

Clinical characteristics

a. The incubation period is 2–25 weeks.

b. Acute infection is often mild or asymptomatic and is rarely diagnosed in this phase.

c. More likely to cause chronic hepatitis, resulting in cirrhosis, than HBV.

d. One of the most common reasons for liver transplant in the United States

Hepatitis C Virus (HCV)

Diagnosis

a. Elevated liver enzymes

b. Serologic indicators (anti-HCV and HCV antigen) and NAATs

c. The virus has not been grown in cell cultures.

Hepatitis C Virus (HCV)

• Contains RNA, and virions range in size from 32 to 34 nm.

• Spread by the fecal-oral route, often in contaminated water.

• It is the most common cause of hepatitis in some countries with poor sanitation.

• Diagnosis: Serology

Hepatitis E virus (HEV)

• Contains RNA and has an envelope.

• It is in the same family, Flaviviridae, as HCV.

• Although it is most commonly transmitted by contact with blood, it can also be sexually transmitted and transmitted from mother to children. Infection seems to be relatively common worldwide, but HGV is believed to be nonpathogenic.

Hepatitis G virus (HGV)