Why do we fall ill? (CBSE-IX)

Syphilis is a bacterial infection that's typically spread through sexual contact.It most commonly begins as a painless sore, usually in the area of your genitals, rectum, or mouth.The infection spreads from person to person through contact with these sores by the skin or mucous membranes.

Bacteria, viruses, and fungi are microorganisms (pathogens), whereas worms are multicellular parasites (helminths), making them the odd one out in a microbiological context.

Antibiotics are effective against bacteria but do not work against viruses, as viruses lack the cellular machinery that antibiotics target.

Communicable diseases are infectious diseases that can spread from one person to another. Malaria and AIDS are both communicable diseases, making options B and C incorrect.

Viruses are obligate intracellular parasites, meaning they must invade and live inside host cells to replicate.

Common cold, pneumonia, and tuberculosis are typically caused by pathogens that can be transmitted through respiratory droplets or air, whereas AIDS is transmitted through specific bodily fluids, making it the odd one out.

Cholera is caused by the bacterium Vibrio cholerae and is primarily transmitted through contaminated water, classifying it as a water-borne disease.

The common cold is a communicable disease (spreads through droplets) and is also an acute disease (short duration), making both 1 and 3 correct.

Tuberculosis is caused by bacteria that spread through the air when an infected person coughs or sneezes. Because it can be transmitted from person to person, it is classified as a communicable disease.

HIV/AIDS is transmitted through the exchange of specific bodily fluids, including blood, breast milk, and during pregnancy or childbirth from mother to child. All listed methods are recognized pathways for transmission.

In epidemiology, a vector is an organism, often an insect or other arthropod, that transmits a pathogen from an infected host to another. The term 'intermediaries' describes this role of carrying the disease agent.

Only female mosquitoes bite humans because they require the protein found in blood to develop their eggs. Male mosquitoes feed exclusively on plant nectar.

Mosquitoes are the most common vectors for many diseases, including malaria, dengue, and Zika. They are highly efficient at transmitting pathogens between human hosts.

Mosquitoes are attracted to warm-blooded animals because they rely on heat and chemical cues like carbon dioxide to locate their hosts. Humans and other mammals are their primary targets.

Bacteria can enter the body through various routes and target different organs, including the digestive system (gut) and the liver. Many foodborne or waterborne pathogens affect these specific areas.

HIV primarily targets and replicates within the immune system, specifically infecting CD4 T cells. These cells are found throughout the body, but the virus is highly concentrated in the lymph nodes, which serve as reservoirs for the infection.

Japanese encephalitis is a viral infection that causes inflammation of the brain, leading to symptoms like high fever, headache, and confusion. It is colloquially referred to as brain fever.

Malaria is caused by Plasmodium parasites, not a virus. However, in the context of the life cycle of the malaria parasite, it travels to the liver first to multiply before infecting red blood cells.

The lungs are responsible for gas exchange. When they are infected, the primary symptoms involve respiratory distress, such as coughing and difficulty breathing (breathlessness).

Malaria is transmitted to humans through the bite of an infected female Anopheles mosquito. The parasite is injected into the bloodstream during the bite.

Jaundice is a condition characterized by the yellowing of the skin and eyes, caused by an accumulation of bilirubin. This occurs when the liver is unable to properly process or excrete bilirubin.

Swelling (edema or inflammation) is typically a localized response to injury or infection at the specific site of the problem, rather than a systemic or general effect.

Fever is indeed an elevation in body temperature, the standard normal temperature is approximately 98.6 F, and most fevers are the body's response to an underlying infection.

Inflammation is an immune response that recruits white blood cells (leukocytes) to the site of infection or injury to neutralize and destroy invading microbes.

The brain controls all bodily functions. If it is targeted by a microbe, symptoms can manifest as neurological disturbances, including seizures (fits), loss of consciousness, and severe headaches.