Zoology · Ch 6 — Biology and Human Welfare
Other Infectious Diseases
Other Infectious Diseases
Other Infectious Diseases
Alongside the four major parasitic infections detailed in this chapter, several other infectious diseases caused by bacteria, viruses and fungi are of everyday public-health importance. Each has a specific causative pathogen and specific measures for its prevention (prophylaxis).
Typhoid fever
Typhoid fever is caused by the rod-shaped bacterium Salmonella typhi. It spreads through the faecal–oral route, chiefly via food and water contaminated with the faeces or urine of an infected person or carrier, and is therefore closely linked to poor sanitation. Symptoms include sustained high fever, weakness, abdominal pain, headache and constipation or diarrhoea; the disease can be confirmed by the Widal test. Prophylaxis rests on safe drinking water, proper sewage disposal, food hygiene, and vaccination (the typhoid vaccine) for those at risk.
Pneumonia
Pneumonia is an inflammation of the lung tissue, most commonly caused in bacterial cases by the bacterium Streptococcus pneumoniae (though viruses and fungi can also cause pneumonia). The bacteria infect the alveoli (air sacs) of the lungs, which then fill with fluid, impairing oxygen exchange and producing symptoms such as high fever, chills, cough with mucus, and difficulty in breathing. In severe cases the lips and fingernails may show a bluish tinge from lack of oxygen. Prophylaxis includes good nutrition and general health, avoiding overcrowded and poorly ventilated spaces, and vaccination against S. pneumoniae for vulnerable groups such as young children and the elderly.
Common cold
The common cold is one of the most frequent human infections and is caused chiefly by rhinoviruses. It infects the mucous membrane lining the nose and respiratory passage, producing familiar symptoms such as nasal congestion, watery discharge, sneezing, sore throat, and mild fever, usually resolving on its own within a few days. Because it spreads by droplet infection and by contact with contaminated surfaces, prophylaxis relies on avoiding close contact with infected persons, maintaining good personal hygiene (regular hand-washing), and covering the nose and mouth while sneezing or coughing to limit droplet spread.