Fever

An analog medical thermometer showing a temperature of 38.7 °C or 101.7 °F
Michael Ancher, "The Sick Girl", 1882, Statens Museum for Kunst
Different fever patterns observed in Plasmodium infections
Hyperthermia: Characterized on the left. Normal body temperature (thermoregulatory set point) is shown in green, while the hyperthermic temperature is shown in red. As can be seen, hyperthermia can be conceptualized as an increase above the thermoregulatory set point.
Hypothermia: Characterized in the center: Normal body temperature is shown in green, while the hypothermic temperature is shown in blue. As can be seen, hypothermia can be conceptualized as a decrease below the thermoregulatory set point.
Fever: Characterized on the right: Normal body temperature is shown in green. It reads "New Normal" because the thermoregulatory set point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic.

Defined as having a temperature above the normal range due to an increase in the body's temperature set point.

- Fever

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Urinary tract infection

Infection that affects part of the urinary tract.

Multiple white cells seen in the urine of a person with a urinary tract infection using microscopy
Urine may contain pus (a condition known as pyuria) as seen from a person with sepsis due to a urinary tract infection.
Uropathogenic Escherichia coli (UPEC) cells adhered to bladder epithelial cell.
Bladder infection
Multiple bacilli (rod-shaped bacteria, here shown as black and bean-shaped) shown between white blood cells in urinary microscopy. These changes are indicative of a urinary tract infection.

Symptoms of a kidney infection include fever and flank pain usually in addition to the symptoms of a lower UTI.

Meningitis

Acute or chronic inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges.

Meninges of the central nervous system: dura mater, arachnoid mater, and pia mater.
Neck stiffness, Texas meningitis epidemic of 1911–12
Charlotte Cleverley-Bisman developed severe meningococcal meningitis as a young child; in her case, the petechial rash progressed to gangrene and required amputation of all limbs. She survived the disease and became a poster child for a meningitis vaccination campaign in New Zealand.
Streptococcus pneumoniae—a causative bacteria of meningitis (illustration).
Cloudy CSF from a person with meningitis due to Streptococcus
Gram stain of meningococci from a culture showing Gram negative (pink) bacteria, often in pairs
Histopathology of bacterial meningitis: autopsy case of a person with pneumococcal meningitis showing inflammatory infiltrates of the pia mater consisting of neutrophil granulocytes (inset, higher magnification).
Structural formula of ceftriaxone, one of the third-generation cefalosporin antibiotics recommended for the initial treatment of bacterial meningitis.
Disability-adjusted life year for meningitis per 100,000 inhabitants in 2004.
Demography of meningococcal meningitis.
Deaths from meningitis per million persons in 2012

The most common symptoms are fever, headache, and neck stiffness.

Malaria

Mosquito-borne infectious disease that affects humans and other animals.

Malaria parasite connecting to a red blood cell
Main symptoms of malaria
The life cycle of malaria parasites. Sporozoites are introduced by a mosquito bite. They migrate to the liver, where they multiply into thousands of merozoites. The merozoites infect red blood cells and replicate, infecting more and more red blood cells. Some parasites form gametocytes, which are taken up by a mosquito, continuing the life cycle.
Micrograph of a placenta from a stillbirth due to maternal malaria. H&E stain. Red blood cells are anuclear; blue/black staining in bright red structures (red blood cells) indicate foreign nuclei from the parasites.
Electron micrograph of a Plasmodium falciparum-infected red blood cell (center), illustrating adhesion protein "knobs"
The blood film is the gold standard for malaria diagnosis.
Ring-forms and gametocytes of Plasmodium falciparum in human blood
An Anopheles stephensi mosquito shortly after obtaining blood from a human (the droplet of blood is expelled as a surplus). This mosquito is a vector of malaria, and mosquito control is an effective way of reducing its incidence.
Man spraying kerosene oil in standing water, Panama Canal Zone, 1912
Walls where indoor residual spraying of DDT has been applied. The mosquitoes remain on the wall until they fall down dead on the floor.
A mosquito net in use.
An advertisement for quinine as a malaria treatment from 1927.
Deaths due to malaria per million persons in 2012
Past and current malaria prevalence in 2009
Ancient malaria oocysts preserved in Dominican amber
British doctor Ronald Ross received the Nobel Prize for Physiology or Medicine in 1902 for his work on malaria.
Chinese medical researcher Tu Youyou received the Nobel Prize for Physiology or Medicine in 2015 for her work on the antimalarial drug artemisinin.
Artemisia annua, source of the antimalarial drug artemisinin
U.S. Marines with malaria in a field hospital on Guadalcanal, October 1942
Members of the Malaria Commission of the League of Nations collecting larvae on the Danube delta, 1929
1962 Pakistani postage stamp promoting malaria eradication program
Malaria clinic in Tanzania
Child with malaria in Ethiopia
World War II poster

Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches.

Common cold

Viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx.

A representation of the molecular surface of one variant of human rhinovirus
Woman with symptoms of the common cold
Coronaviruses are a group of viruses known for causing the common cold. They have a halo or crown-like (corona) appearance when viewed under an electron microscope.
The common cold is a disease of the upper respiratory tract.
Poster from 1937 encouraging citizens to "consult your physician" for treatment of the common cold
A British poster from World War II describing the cost of the common cold

These may include coughing, sore throat, runny nose, sneezing, headache, and fever.

Ibuprofen

Example of some 200 mg ibuprofen tablets
The Royal Society of Chemistry blue plaque at BioCity Nottingham
A bottle of generic ibuprofen

Ibuprofen is a medication in the nonsteroidal anti-inflammatory drug (NSAID) class that is used for treating pain, fever, and inflammation.

Paracetamol

Important pathways of paracetamol metabolism.
Classical methods for the production of paracetamol.
Paracetamol crystals (crystallized from an aqueous solution) under a microscope.
Julius Axelrod (pictured) and Bernard Brodie demonstrated that acetanilide and phenacetin are both metabolized to paracetamol, which is a better-tolerated analgesic.

Paracetamol, also known as acetaminophen, is a medication used to treat fever and mild to moderate pain.

Vasculitis

Group of disorders that destroy blood vessels by inflammation.

Petechia and purpura on the lower limb due to medication-induced vasculitis.
Micrograph showing a vasculitis (eosinophilic granulomatosis with polyangiitis). H&E stain.
Severe vasculitis of the major vessels, displayed on FDG-PET/CT

General symptoms: Fever, unintentional weight loss

Hyperthermia

Condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation.

An analog medical thermometer showing a temperature of 38.7 C
A summary of the differences between hyperthermia, hypothermia, and fever.
Hyperthermia: Characterized on the left. Normal body temperature (thermoregulatory set-point) is shown in green, while the hyperthermic temperature is shown in red. As can be seen, hyperthermia can be considered an increase above the thermoregulatory set-point.
Hypothermia: Characterized in the center: Normal body temperature is shown in green, while hypothermic temperature is shown in blue. As can be seen, hypothermia can be conceptualized as a decrease below the thermoregulatory set-point.
Fever: Characterized on the right: Normal body temperature is shown in green. It reads "New Normal" because the thermoregulatory set-point has risen. This has caused what was the normal body temperature (in blue) to be considered hypothermic.

Hyperthermia differs from fever in that the body's temperature set point remains unchanged.

Perspiration

Production of fluids secreted by the sweat glands in the skin of mammals.

Droplets of perspiration on the skin
A man in a sweat-drenched shirt, after some physical exertion.
The evaporation of sweat on the skin cools the body.
Beads of sweat emerging from eccrine glands

If it is accompanied by unexplained weight loss or fever or by palpitations, shortness of breath, or chest discomfort, it suggests serious illness.

Human body temperature

Typical temperature range found in humans.

A medical thermometer showing a temperature reading of 38.7 °C
Diurnal variation in body temperature, ranging from about 37.5 °C from 10 a.m. to 6 p.m., and falling to about 36.4 °C from 2 a.m. to 6 a.m. (Based on figure in entry for 'Animal Heat' in 11th edition of the Encyclopædia Britannica, 1910)

Elderly patients may have a decreased ability to generate body heat during a fever, so even a somewhat elevated temperature can indicate a serious underlying cause in geriatrics.