VIRAL DISEASES
Science
Introduction
- Viral diseases are caused by viruses, which are microscopic infectious agents.
- Viruses contain DNA or RNA enclosed in a protein coat.
- They replicate only inside living host cells.
- Viral replication often damages or destroys host cells.
- Viral diseases pose major public health challenges due to high transmissibility.
Avian Influenza
- Highly contagious viral disease of birds.
- Affects poultry, wild birds and occasionally humans.
- Influenza viruses are of three types – A, B and C.
- Only type A infects animals and humans (zoonotic).
- Important subtypes include A(H5N1), A(H7N9), A(H9N2).
- Prevention requires strict biosecurity and hygiene.
Rotavirus – Diarrhoea
- Highly contagious virus causing diarrhoea in children.
- Most children infected before 5 years of age.
- Severe cases cause dehydration.
- Exclusive breastfeeding is protective.
- Treatment focuses on rehydration.
Human Papilloma Virus (HPV)
- Sexually transmitted viral infection.
- Major cause of cervical cancer.
- Linked with cancers of anus, vulva, vagina and penis.
- WHO recommends HPV vaccines (16 and 18).
- Screening helps prevent cervical cancer.
Hepatitis B
- Viral infection affecting the liver.
- Causes acute and chronic disease.
- Transmitted through blood, body fluids and childbirth.
- Preventable through vaccination.
HIV
- Attacks CD4 T cells of immune system.
- Weakens immunity permanently.
- Transmitted through body fluids.
- Treated with Anti-Retroviral Therapy.
Measles
- Highly contagious viral disease.
- Mainly affects children.
- Spread through air and contact.
- Preventable by vaccination.
Rabies
- Vaccine-preventable viral disease.
- Dogs cause 99% of human cases.
- Immediate wound washing is critical.
- WHO targets zero deaths by 2030.
Smallpox
- Caused by variola virus.
- One of the deadliest diseases historically.
- Eradicated globally in 1980.
Polio
- Highly infectious viral disease.
- Affects children under 5.
- Spread through faeco-oral route.
- Almost eradicated globally.
Rubella
- Viral infection in children and young adults.
- Causes congenital birth defects.
- Preventable by vaccination.
Chickenpox
- Caused by Varicella-Zoster Virus.
- Highly contagious.
- Characterised by itchy rash.
Japanese Encephalitis
- Mosquito-borne viral disease.
- High fatality in severe cases.
- Vaccination recommended in endemic areas.
Zika Viral Fever
- Spread by Aedes mosquito.
- Dangerous for pregnant women.
- Causes microcephaly.
Yellow Fever
- Mosquito-borne viral disease.
- Causes jaundice.
- Vaccine available – 17D.
MERS
- Caused by MERS coronavirus.
- Camels are major reservoir.
- Limited human transmission.
SARS
- Caused by coronavirus.
- Identified in 2003.
- Spread through droplets.
COVID-19
- Caused by SARS-CoV-2.
- Spread via respiratory droplets.
- Vaccines include Covaxin, Covishield and Sputnik V.
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Subject: Science
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