Lecture 5 6 7

Learning Outcomes for Lecture 6: DSRNA Viruses

• Students will be able to describe the pathogenesis of Reoviridae, specifically rotavirus.

Reoviridae Family

• Reovirus, a family of viruses found in human and animal respiratory and enteric tracts.
• Infections are frequently asymptomatic.
• Rotavirus is the most studied member of this family.
• It causes gastroenteritis.
• Rotavirus is resistant to chlorine treatment.
• Rotavirus infections are easily transmitted between animals and humans.

Rotavirus Virion

• Rotavirus virion is comprised of 3 layers of capsids: inner, intermediate, and outer.
• Isolated from fecal samples from humans and animals
• The virion is naked and icosahedral.
• It has 11 RNA segments.
• Channels are present in the inner and intermediate layers of the capside for RNA transcript movement.

Why is Rotavirus Triple Layered?

• Double-stranded RNA (dsRNA) is a potent inducer of apoptosis, interferon production, and RNA silencing.
• The enclosed dsRNA in the rotavirus structure protects it from these effects.
• Transcription of the dsRNA in rotavirus happens in the inner capside layer rather than the cytoplasm.
• It is difficult for the RNA to be released to the surrounding environment due to strong inflammatory responses.

Rotavirus Disease

• Rotavirus contributes to a significant number of infant and young children's deaths yearly.
• In Malaysia, it is estimated to be 22-50% of all diarrheal cases in children.
• Enterocytes on the villi of the small intestine are destroyed.
• Rotavirus causes a decrease in the absorption of water, sugar, and salts.
• It inhibits water and salts' absorption, resulting in diarrhea and dehydration.
• Treatment involves rehydration through sugar and salts.

Rotavirus Infection Anatomy

• The rotavirus infects the villous epithelium of the small intestine, especially the proximal areas.

• The virus replicates and releases infectious particles in the distal small intestine.

• The primary symptom is induced by the viral enterotoxin NSP4.

• The virus can easily infect older individuals due to immunodeficiency.

Learning Outcomes for Lecture 7: (+) ssRNA Viruses

• Students will be able to describe the pathogenesis of (+) ssRNA viruses.

Picornaviridae Family

• A family of small RNA viruses infecting humans and animals.
• Known genera of picornaviruses include hepatovirus (liver), enterovirus (intestine), rhinovirus (nose), and aphthovirus (vesicles in mouths).
• Different picornavirus types infect different parts of the body.

Picornavirus Diseases

• Hepatitis A virus is a significant cause of liver infection.
• Polio virus is responsible for polio, which can cause paralysis and other neurological complications.
• Coxsackieviruses cause diseases such as hand-foot-and-mouth disease, and similar syndromes.
• Enterovirus 70 and 71 can cause diseases prevalent in East Asia and Southeast Asia.
• Rhinovirus is responsible for common cold.
• Foot and mouth disease is a foot-and-mouth disease in livestock and mammals.

Picornaviruses HiJack Host Systems

• They inhibit the host's protein synthesis, transcription process by blocking RNA polymerase and transportation of host mRNA.

Flaviviridae Family

• The family of viruses includes West Nile virus, dengue virus, and yellow fever virus.
• West Nile virus is most commonly encountered in the Northern part of the Americas.
• West Nile causes brain infections which may lead to death or severe neurological problems such as encephalitis, and meningitis.
• Dengue virus is spread by the Aedes mosquito.
• Yellow fever is spread to humans from mosquitos.
• It can be potentially fatal.

Coronaviridae Family

• This family of viruses infects humans, commonly causing mild respiratory symptoms.
• The viruses have been identified to cause SARS, MERS, and Covid-19 (Coronavirus disease 2019).
• Symptoms include high fever, headache, body aches, diarrhea, dry cough.
• Primarily spread by close contact.

Togaviridae Family

• This family includes viruses such as equine encephalitis viruses and Chikungunya viruses.
• These viruses are spread by mosquitoes.
• Symptoms include fever, rash, headache, and arthralgia (joint pain).
• The most common symptom includes fever, malaise, headache.

Rubella Virus (German Measles)

• Unvaccinated children and young adults are susceptible to rubella.
• It can have serious consequences, including miscarriages and causing congenital defects.
• The infection is spread through coughing and sneezing.
• Preventable by vaccination.

Rhabdoviridae Family

• This family includes viruses such as rabies viruses.
• The viruses infect mammals, fish, plants, and insects.
• The viruses are spread through bites from infected animals.
• Common illnesses caused by the viruses include encephalitis.
• Two types of rabies exist and include furious rabies characterized by symptoms such as headache, fever, irritability, restless, anxiety and dumb rabies characterized by paralysis and a steady decline in the patient's health.
• Rabies can be treated if detected earlier.
• The viruses block host systems by inhibiting host protein synthesis, by inhibiting transcription by host RNA polymerase.
• They also block intracellular transport of host mRNA and inhibit interferon synthesis.

Orthomyxoviridae Family

• This family includes viruses such as influenza A and B viruses.
• These viruses cause seasonal flu epidemics.
• The viruses' high mutation rate causes a significant error rate during viral genome replication.
• The genes responsible for the surface proteins contribute to the development of various subtypes (eg. H1N1, H3N2, H5N1, H7N9).
• Transmission occurs through respiratory droplets via sneezing and coughing.
• Symptoms include fever, cough, sore throat, body aches, fatigue, headaches, and occasionally, vomiting, and diarrhea, especially in children.
• There is no known cure for the flu.

Paramyxoviridae Family

• This family includes viruses like measles virus.
• It is a highly contagious respiratory disease spread through contaminated air droplets.
• Prevention requires a high percentage of herd immunity.
• Symptoms including fever, runny nose, cough, red eyes, rash all over the body.
• Some of the complications can include pneumonia, diarrhea, and ear infections, prevalent in adults and children.
• It is preventable by vaccination.

Henipavirus

• Henipaviruses are found in bats and pigs and can be passed from these animals to humans.
• Some symptoms include encephalitis and respiratory-related illness.
• Prevention involves preventing contact with animals (especially pigs) and practicing proper sanitation.

Filoviridae Family

• This family of viruses includes Ebola and Marburg viruses.
• It is a cause of severe haemorrhagic fevers with a high fatality rate.
• Transmission occurs through contact with an infected animal or via bodily fluid contact with an infected individual.
• It can be transmitted from an animal to another animal through contact.

Bunyaviridae Family

• This family of viruses includes certain hantaviruses found in Asia and the New World.
• The viruses can lead to haemorrhagic fever, particularly Renal Syndrome (HFRS) and the Pulmonary Syndrome (HPS).
• The first identified hantavirus was Sin Nombre.
• Rodent control is a key strategy to prevent Hantavirus infections.