Virology Quiz on RNA Viruses

RNA Viruses

• RNA viruses are a group of viruses with RNA as their genetic material.
• Common RNA viruses include Coronaviruses (OC43 229E), Enterovirus, HAV, HCV, HEV, HIV, HTLV, Human metapneumovirus, Influenza A, Influenza B, Measles, MERS, Mumps, Norovirus, Parainfluenza, Polio, Rhinoviruses, Rotavirus, RSV, Rubella (German Measles), SARS, SARS-CoV-2.
• Learning objectives include describing symptoms, diagnosis, and treatment of common RNA viruses.

Common Cold Symptoms

• Common cold symptoms typically present similarly, including: sneezing; stuffy nose; runny nose; sore throat; coughing; post-nasal drip; watery eyes; fever (rare); chills (rare).
• Doctors often recommend monitoring symptom severity, using inhalers (more readily prescribed now), and watching for rashes.
• Breathing and temperature checks are key aspects of monitoring.

Coronaviruses Background

• Coronaviruses are a family of enveloped, positive-sense, single-stranded RNA viruses.
• They have the largest genomes of all RNA viruses (~30kb).
• They infect humans, other mammals, some birds, livestock, and pets.
• They account for approximately 10-15% of upper respiratory tract infections.

Nidovirales Coronaviridae

• Nidoviruses are named for the nested subgenomic mRNAs generated during infection.
• Coronaviruses are enveloped viruses (100-150nm).
• Coronaviruses have RNA genomes.

Types of Infections from Coronaviruses

• Coronavirus infections can affect the respiratory system (human OC43, 229E; avian IBV), the brain (neurotropic MHV, demyelinating), the liver (MHV), or the gastrointestinal tract (procine TGEV, avian IBV, MHV).

Human Coronaviruses: Timeline

• Common cold coronaviruses OC43 and 229E have been present since the 1980s.
• SARS-CoV emerged in 2002, causing 812 deaths (10% case fatality rate).
• HKU1, NL63, and Croup affected people in 2004 and 2005.
• MERS-CoV emerged in 2012, causing 866 deaths (34% case fatality rate).
• SARS-CoV-2 (COVID-19) emerged in 2019, leading to over 6.7 million deaths (1% case fatality rate initially, 2-3 % originally-note this is an important distinction).
• Seasonal influenza typically infects between 250,000 and 500,000 people annually.

Human Metapneumovirus

• Human Metapneumovirus (hMPV) can cause upper and lower respiratory disease in individuals of all ages, particularly young children and older adults.
• Symptoms include cough, fever, nasal congestion, bronchitis, or pneumonia.
• There is no specific treatment or vaccine for hMPV.

Respiratory Syncytial Virus (RSV)

• RSV usually causes mild cold-like symptoms.
• Most people recover within 1-2 weeks, but can be serious in infants and older adults.
• Symptoms include runny nose, decreased appetite, coughing, sneezing, fever, and wheezing.
• Almost all children have had RSV by age two.
• There is no specific treatment or vaccine currently available, but an mRNA vaccine for adults is currently being developed.

Influenza

• 75-95% of influenza cases are influenza A, and the remaining 5-25% are influenza B.
• Influenza affects the nose, throat, and lungs, and can cause mild to severe illness.
• Symptoms include fever (not everyone experiences it), cough, sore throat, runny/stuffy nose, muscle aches, headache, fatigue, and sometimes vomiting and diarrhea.
• Flu patients are more susceptible to bacterial infections.
• Cytokine storm syndrome (excessive inflammatory response) can aggravate respiratory failure and lead to systemic organ failure.
• Influenza viruses have segmented genomes, allowing for reassortment, which affects vaccine design and effectiveness yearly.
• Oseltamivir (Tamiflu) is a neuraminidase inhibitor used to treat influenza A and B but is not often recommended due to resistance.

Rotavirus

• Rotavirus is a double-stranded RNA virus of the Reoviridae family.
• Symptoms include watery diarrhea, vomiting, fever, and abdominal pain.
• There is no virus-specific treatment.
• There is a 2-dose vaccine available.

Norovirus

• Norovirus is a single-stranded RNA virus of the Caliciviridae family.
• Symptoms include diarrhea, vomiting, nausea, and stomach pain.
• There is no virus-specific treatment or vaccine available.

Measles Virus

• Measles symptoms begin 10-14 days after exposure, characterized by a four-day fever, cough, coryza (head cold, fever, sneezing), conjunctivitis, and a typical rash.
• Diagnosis involves checking for fever for at least 3 days, and one of the "3C's", and confirming the presence of measles virus antibodies or RNA from respiratory samples.
• Complications include diarrhea, pneumonia, bronchitis, and brain inflammation (rarely subacute sclerosing panencephalitis) and corneal ulceration.
• Treatment involves managing symptoms (e.g., ibuprofen) and providing airway dilators if necessary. Vitamin A may be given to reduce the risk of blindness.

Human Immunodeficiency Virus (HIV)

• HIV is the etiological agent responsible for AIDS.
• HIV was discovered in 1984.
• Approximately 40 million people globally have HIV, with about 50,000 cases in Canada.
• No vaccine is available.
• Approximately 30 drugs are currently in use for HIV treatment. These medications inhibit reverse transcriptase, protease, entry, and integrase.
• Acute HIV infection is rarely diagnosed except in high-risk individuals who are frequently tested. Late diagnosis is common, often due to lack of symptoms, especially in rural areas.
• Chronic HIV infection symptoms include nausea, vomiting, persistent diarrhea, rapid weight loss, rashes, sores/lesions, persistent infections, and neurological complications including memory loss and confusion.
• The course of untreated HIV is characterized by progressive decline in CD4+ T cells and increasing viral load.

Hepatitis C Virus (HCV)

• 70-85% of untreated HCV infections become chronic.
• 15-20% of untreated HCV infections develop into hepatocellular carcinoma.
• Approximately 71 million people worldwide are infected with HCV, and 270,000 Canadians are infected (0.8 % of the Canadian population, or 2-4 people per 100,000 people).
• About 3,200 to 5,000 new HCV cases emerge each year in Canada.
• HCV transmission commonly occurs through injection drug use (60%), but other routes exist (sexual transmission, transfusion, and unknown sources).
• Chronic HCV symptoms can include fatigue, muscle aches, loss of appetite, weakness, weight loss, blood clotting problems, and liver-specific problems like cirrhosis, fibrosis, and hepatocellular carcinoma.
• Interferon (IFN) and ribavirin were once the only treatment, but are less effective due to genotype specificity and poor tolerability.
• Protease inhibitors, polymerase inhibitors, and NS5A inhibitors have become available since 2011, which significantly improved cure rates (now upwards of 99% in clinical trials and 95% in real-world treatment using cocktails).
• Several HCV treatment drugs are available, including Sofosbuvir (NS5B), Velpatasvir (NS5A), Daclatasvir (NS5A), Ombitasvir (NS5A), Paritaprevir (NS3/4A), Ritonavir (CYP3A), Dasabuvir (NS5B non-nuc), Ledipasvir (NS5A), and Sofosbuvir (NS5B).
• HCV was discovered in 1989.