Why do we fall ill? (CBSE-IX)

Sneezing releases respiratory droplets into the air, which can carry pathogens and lead to the spread of droplet infections.

Goiter is an enlargement of the thyroid gland, which is primarily caused by a deficiency of iodine in the diet.

Hepatitis B is generally considered more dangerous than Hepatitis A because it is more likely to lead to chronic infection, liver cirrhosis, and liver cancer.

Hydrophobia, meaning fear of water, is a classic symptom of rabies infection in humans, and the term is often used as a synonym for the disease.

Acquired diseases are those that develop after birth, typically due to environmental factors or infection, whereas congenital diseases are present since birth.

Interferons are signaling proteins released by host cells in response to the presence of several viruses, acting as antiviral agents.

A pathogen is the disease-causing agent itself (like a virus or bacterium), whereas a vector is an organism that transmits the pathogen (like a mosquito).

Cholera is caused by the bacterium Vibrio cholerae, and malaria is caused by a protozoan parasite of the genus Plasmodium.

Mycobacterium tuberculosis is the bacterium responsible for causing tuberculosis (TB).

The HIV virus, which causes AIDS, is a retrovirus that contains single-stranded RNA as its genetic material, not DNA.

Female Anopheles mosquitoes are the primary vectors for the transmission of malaria parasites.

Eggs are considered a complete food source, containing high-quality proteins, various vitamins (like B12), and minerals (like selenium).

Mosquitoes that transmit malaria typically breed in stagnant, still water where they can lay their eggs.

Leprosy is a chronic infectious disease caused by the bacterium Mycobacterium leprae.

Antigens are foreign substances that the immune system recognizes, triggering the production of specific antibodies to neutralize them.

Interferons are a group of signaling proteins made and released by host cells in response to the presence of several viruses.

T-lymphocytes are generally categorized into four main functional types: helper T cells, cytotoxic T cells, memory T cells, and regulatory T cells.

Typhoid fever is a systemic infection caused by Salmonella Typhi. Common symptoms include high fever, abdominal pain or tenderness, and malaise.

Cytotoxic T cells are specialized immune cells that destroy infected or cancerous cells, earning them the name killer cells.

Flu is the common name for influenza, a viral infection that attacks the respiratory system.

Hepatitis is an inflammation of the liver. Jaundice, which is the yellowing of the skin and eyes, is a common clinical manifestation of liver dysfunction caused by hepatitis.

Antigens are molecules that the immune system recognizes as foreign, triggering an immune response such as the production of antibodies.