MCB 404: Medical Virology - Arboviruses

Arboviruses

• Arboviruses are viral infections transmitted to humans by arthropods such as fleas, ticks, and mosquitoes.
• Key genera causing human infections include:
  • Flavivirus: Yellow fever, West Nile virus, Zika virus, Dengue fever, Japanese encephalitis.
  • Togavirus: Ross River virus, Eastern equine virus, Western equine virus.
  • Bunyavirus: California encephalitis, La Crosse virus, Jamestown Canyon virus.

Transmission

• Spread through insect bites, blood transfusion, organ transplant, sexual contact, pregnancy, and childbirth.

Clinical Features

• Neuroinvasive diseases: Symptoms include meningitis, fever, headache, stiff neck, muscle pain, confusion, weakness, seizures.
• Non-neuroinvasive diseases: Symptoms include fever, headache, muscle aches, joint pain, gastrointestinal distress, rash.

Epidemiology

• Globally distributed; warm climates support year-round transmission.

Diagnosis

• Common methods include ELISA and Polymerase Chain Reaction (PCR).

Treatment

• Most infections require supportive care; no specific antiviral treatments.

Prevention and Control

• Vaccines available for some arboviruses (e.g., Japanese encephalitis, yellow fever).
• Preventive measures include using insect repellent and wearing protective clothing.

Coronaviruses

• A large family of respiratory viruses includes COVID-19, MERS, and SARS.
• These viruses often circulate among animals like camels, cats, and bats.
• COVID-19 (SARS-CoV-2) emerged in Wuhan, China in 2019 and was declared a pandemic.

Transmission

• Spread through respiratory droplets from coughs/sneezes, direct contact, surface contact, or touching face after contacting contaminated surfaces.

Clinical Features

• Symptoms commonly include fever, cough, headache, runny nose, and severe cases lead to pneumonia or bronchitis, particularly in vulnerable populations.

Epidemiology

• Winter outbreaks are common; immunity does not last, leading to potential re-infections.

Diagnosis

• Diagnosed via ELISA and PCR.

Treatment

• Symptomatic relief includes pain medications, hydration, and rest.

Prevention and Control

• Preventative measures: Vaccination, wearing masks, hand hygiene, and avoiding close contact with sick individuals.

Retroviruses

• Retroviruses insert a DNA copy of their RNA genome into the host cell, using reverse transcriptase.
• Key types include HIV (causes AIDS), HTLV (causes leukemia), and benign spumaviruses.

Transmission

• Mainly through vertical transmission (mother to child) during childbirth or breastfeeding.
• Other routes include unprotected sexual contact and transmission via blood or medical procedures.

Clinical Features

• Initial flu-like symptoms (seroconversion illness) such as fever and malaise occur 2-6 weeks post-exposure.
• Symptomatic HIV presents with weight loss, high fever, diarrhea, and frequent opportunistic infections.

Diagnosis

• Identified through ELISA and PCR.

Treatment

• Treated with antiretroviral drugs; HAART employs a combination of multiple drugs to combat HIV.