Fever of other and unknown origin (R50)

Browse all the diagnosis codes used for fever of other and unknown origin (r50). For easy navigation, the diagnosis codes are sorted in alphabetical order and grouped by sections. Each section is clearly marked with its description, and the corresponding three-digit code range. This format makes it simple to browse diagnosis codes in this chapter or section and find what you're looking for. We've also added green checkmark icons to label billable codes, and red warning icons for non-billable ones. This makes it easy to identify which codes can be billed.

Clinical Information

Adenovirus Infections, Human - Respiratory and conjunctival infections caused by 33 identified serotypes of human adenoviruses.

Bartonella Infections - Infections by the genus BARTONELLA. Bartonella bacilliformis can cause acute febrile anemia, designated Oroya fever, and a benign skin eruption, called verruga peruana. BARTONELLA QUINTANA causes TRENCH FEVER, while BARTONELLA HENSELAE is the etiologic agent of bacillary angiomatosis (ANGIOMATOSIS, BACILLARY) and is also one of the causes of CAT-SCRATCH DISEASE.

Bartonella quintana - A species of gram-negative bacteria in which man is the primary host and the human body louse, Pediculus humanus, the principal vector. It is the etiological agent of TRENCH FEVER.

Blackwater Fever - A complication of MALARIA, FALCIPARUM characterized by the passage of dark red to black urine.

Boutonneuse Fever - A febrile disease of the Mediterranean area, the Crimea, Africa, and India, caused by infection with RICKETTSIA CONORII.

Brucellosis - Infection caused by bacteria of the genus BRUCELLA mainly involving the MONONUCLEAR PHAGOCYTE SYSTEM. This condition is characterized by fever, weakness, malaise, and weight loss.

Cat-Scratch Disease - A self-limiting bacterial infection of the regional lymph nodes caused by AFIPIA felis, a gram-negative bacterium recently identified by the Centers for Disease Control and Prevention and by BARTONELLA HENSELAE. It usually arises one or more weeks following a feline scratch, with raised inflammatory nodules at the site of the scratch being the primary symptom.

Chemotherapy-Induced Febrile Neutropenia - FEVER accompanied by a significant reduction in NEUTROPHIL count associated with CHEMOTHERAPY.

Chikungunya Fever - An acute infection caused by a mosquito-borne alphavirus CHIKUNGUNYA VIRUS characterized by RASH; FEVER; JOINT PAINS; CONJUNCTIVITIS; MENINGOENCEPHALITIS; LYMPHOPENIA; and THROMBOCYTOPENIA.

Colorado Tick Fever - A febrile illness characterized by chills, aches, vomiting, leukopenia, and sometimes encephalitis. It is caused by the COLORADO TICK FEVER VIRUS, a reovirus transmitted by the tick Dermacentor andersoni.

Colorado tick fever virus - A species of COLTIVIRUS transmitted by the tick DERMACENTOR andersonii and causing fever, chills, aching head and limbs, and often vomiting. It occurs in the northwestern United States, except the Pacific Coast.

Dengue - An acute febrile disease transmitted by the bite of AEDES mosquitoes infected with DENGUE VIRUS. It is self-limiting and characterized by fever, myalgia, headache, and rash. SEVERE DENGUE is a more virulent form of dengue.

Dengue Virus - A species of the genus FLAVIVIRUS which causes an acute febrile and sometimes hemorrhagic disease in man. Dengue is mosquito-borne and four serotypes are known.

Drug Fever - Drug-induced fever.

Ephemeral Fever - An Ephemerovirus infection of cattle caused by bovine ephemeral fever virus (EPHEMERAL FEVER VIRUS, BOVINE). It is characterized by respiratory symptoms, increased oropharyngeal secretions and lacrimation, joint pains, tremor, and stiffness.

Equine Infectious Anemia - Viral disease of horses caused by the equine infectious anemia virus (EIAV; INFECTIOUS ANEMIA VIRUS, EQUINE). It is characterized by intermittent fever, weakness, and anemia. Chronic infection consists of acute episodes with remissions.

Febrile Neutropenia - Fever accompanied by a significant reduction in the number of NEUTROPHILS.

Feline Panleukopenia - A highly contagious DNA virus infection of the cat family, characterized by fever, enteritis and bone marrow changes. It is also called feline ataxia, feline agranulocytosis, feline infectious enteritis, cat fever, cat plague, and show fever. It is caused by FELINE PANLEUKOPENIA VIRUS or the closely related MINK ENTERITIS VIRUS or CANINE PARVOVIRUS.

Fever - An abnormal elevation of body temperature, usually as a result of a pathologic process.

Fever of Unknown Origin - Fever in which the etiology cannot be ascertained.

Flavivirus - A genus of FLAVIVIRIDAE containing several subgroups and many species. Most are arboviruses transmitted by mosquitoes or ticks. The type species is YELLOW FEVER VIRUS.

Hemorrhagic Fever with Renal Syndrome - An acute febrile disease occurring predominately in Asia. It is characterized by fever, prostration, vomiting, hemorrhagic phenonema, shock, and renal failure. It is caused by any one of several closely related species of the genus ORTHOHANTAVIRUS. The most severe form is caused by HANTAAN VIRUS whose natural host is the rodent Apodemus agrarius. Milder forms are caused by SEOUL VIRUS and transmitted by the rodents Rattus rattus and R. norvegicus, and the PUUMALA VIRUS with transmission by Clethrionomys galreolus.

Hemorrhagic Fever, American - Diseases caused by American hemorrhagic fever viruses (ARENAVIRUSES, NEW WORLD).

Hemorrhagic Fever, Crimean - A severe, often fatal disease in humans caused by the Crimean-Congo hemorrhagic fever virus (HEMORRHAGIC FEVER VIRUS, CRIMEAN-CONGO).

Hemorrhagic Fever, Omsk - Infection with the Omsk hemorrhagic fever virus, a Flavivirus.

Hemorrhagic Fevers, Viral - A group of viral diseases of diverse etiology but having many similar clinical characteristics; increased capillary permeability, leukopenia, and thrombocytopenia are common to all. Hemorrhagic fevers are characterized by sudden onset, fever, headache, generalized myalgia, backache, conjunctivitis, and severe prostration, followed by various hemorrhagic symptoms. Hemorrhagic fever with kidney involvement is HEMORRHAGIC FEVER WITH RENAL SYNDROME.

Hepatitis D - INFLAMMATION of the LIVER in humans caused by HEPATITIS DELTA VIRUS, a defective RNA virus that can only infect HEPATITIS B patients. For its viral coating, hepatitis delta virus requires the HEPATITIS B SURFACE ANTIGENS produced by these patients. Hepatitis D can occur either concomitantly with (coinfection) or subsequent to (superinfection) hepatitis B infection. Similar to hepatitis B, it is primarily transmitted by parenteral exposure, such as transfusion of contaminated blood or blood products, but can also be transmitted via sexual or intimate personal contact.

Hereditary Autoinflammatory Diseases - Hereditary inflammation conditions, characterized by recurrent episodes of systemic inflammation. Common symptoms include recurrent fever, rash, arthritis, fatigue, and secondary AMYLOIDOSIS. Hereditary autoinflammatory diseases are associated with mutations in genes involved in regulation of normal inflammatory process and are not caused by AUTOANTIBODIES, or antigen specific T-LYMPHOCYTES.

Herpes Labialis - Herpes simplex, caused by type 1 virus, primarily spread by oral secretions and usually occurring as a concomitant of fever. It may also develop in the absence of fever or prior illness. It commonly involves the facial region, especially the lips and the nares. (Dorland, 27th ed.)

Hyperthermia - An abnormal elevation of body temperature, usually as a result of inability to regulate core body temperature due to non-pathologic factors.

Hyperthermia, Induced - Abnormally high temperature intentionally induced in living things regionally or whole body. It is most often induced by radiation (heat waves, infra-red), ultrasound, or drugs.

Infectious Mononucleosis - A common, acute infection usually caused by the Epstein-Barr virus (HERPESVIRUS 4, HUMAN). There is an increase in mononuclear white blood cells and other atypical lymphocytes, generalized lymphadenopathy, splenomegaly, and occasionally hepatomegaly with hepatitis.

Jaundice - A clinical manifestation of HYPERBILIRUBINEMIA, characterized by the yellowish staining of the SKIN; MUCOUS MEMBRANE; and SCLERA. Clinical jaundice usually is a sign of LIVER dysfunction.

Lassa Fever - An acute febrile human disease caused by the LASSA VIRUS.

Lassa virus - A species of ARENAVIRUS, part of the Old World Arenaviruses (ARENAVIRUSES, OLD WORLD), and the etiologic agent of LASSA FEVER. LASSA VIRUS is a common infective agent in humans in West Africa. Its natural host is the multimammate mouse Mastomys natalensis.

Legionnaires' Disease - An acute, sometimes fatal, pneumonia-like bacterial infection characterized by high fever, malaise, muscle aches, respiratory disorders and headache. It is named for an outbreak at the 1976 Philadelphia convention of the American Legion.

Leishmania donovani - A parasitic hemoflagellate of the subgenus Leishmania leishmania that infects man and animals and causes visceral leishmaniasis (LEISHMANIASIS, VISCERAL). The sandfly genera Phlebotomus and Lutzomyia are the vectors.

Leishmaniasis, Visceral - A chronic disease caused by LEISHMANIA DONOVANI and transmitted by the bite of several sandflies of the genera Phlebotomus and Lutzomyia. It is commonly characterized by fever, chills, vomiting, anemia, hepatosplenomegaly, leukopenia, hypergammaglobulinemia, emaciation, and an earth-gray color of the skin. The disease is classified into three main types according to geographic distribution: Indian, Mediterranean (or infantile), and African.

Leptospira - A genus of aerobic, helical spirochetes, some species of which are pathogenic, others free-living or saprophytic.

Leptospirosis - Infections with bacteria of the genus LEPTOSPIRA.

Malaria - A protozoan disease caused in humans by four species of the PLASMODIUM genus: PLASMODIUM FALCIPARUM; PLASMODIUM VIVAX; PLASMODIUM OVALE; and PLASMODIUM MALARIAE; and transmitted by the bite of an infected female mosquito of the genus ANOPHELES. Malaria is endemic in parts of Asia, Africa, Central and South America, Oceania, and certain Caribbean islands. It is characterized by extreme exhaustion associated with paroxysms of high FEVER; SWEATING; shaking CHILLS; and ANEMIA. Malaria in ANIMALS is caused by other species of plasmodia.

Malignant Catarrh - A herpesvirus infection of cattle characterized by catarrhal inflammation of the upper respiratory and alimentary epithelia, keratoconjunctivitis, encephalitis and lymph node enlargement. Syn: bovine epitheliosis, snotsiekte.

Malignant Hyperthermia - Rapid and excessive rise of temperature accompanied by muscular rigidity following general anesthesia.

Marburg Virus Disease - An RNA virus infection of rhesus, vervet, and squirrel monkeys transmissible to man.

Neutrophils - Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes.

Orientia tsutsugamushi - A gram-negative, rod-shaped to coccoid bacterium. It is the etiologic agent of SCRUB TYPHUS in humans and is transmitted by mites from rodent reservoirs.

Ornithodoros - A genus of softbacked TICKS, in the family ARGASIDAE, serving as the vector of BORRELIA, causing RELAPSING FEVER, and of the AFRICAN SWINE FEVER VIRUS.

Paratyphoid Fever - A prolonged febrile illness commonly caused by several Paratyphi serotypes of SALMONELLA ENTERICA. It is similar to TYPHOID FEVER but less severe.

Parturient Paresis - A disease of pregnant and lactating cows and ewes leading to generalized paresis and death. The disease, which is characterized by hypocalcemia, occurs at or shortly after parturition in cows and within weeks before or after parturition in ewes.

Pasteurellosis, Pneumonic - Bovine respiratory disease found in animals that have been shipped or exposed to CATTLE recently transported. The major agent responsible for the disease is MANNHEIMIA HAEMOLYTICA and less commonly, PASTEURELLA MULTOCIDA or HAEMOPHILUS SOMNUS. All three agents are normal inhabitants of the bovine nasal pharyngeal mucosa but not the LUNG. They are considered opportunistic pathogens following STRESS, PHYSIOLOGICAL and/or a viral infection. The resulting bacterial fibrinous BRONCHOPNEUMONIA is often fatal.

Pneumonia, Atypical Interstitial, of Cattle - A cattle disease of uncertain cause, probably an allergic reaction.

Q Fever - An acute infectious disease caused by COXIELLA BURNETII. It is characterized by a sudden onset of FEVER; HEADACHE; malaise; and weakness. In humans, it is commonly contracted by inhalation of infected dusts derived from infected domestic animals (ANIMALS, DOMESTIC).

Rat-Bite Fever - A syndrome characterized by recurring fever, rash, and arthralgias occurring days to weeks after a rat bite. The causative agents are either Streptobacillus moniliformis or Spirillum minus.

Relapsing Fever - An acute infection characterized by recurrent episodes of PYREXIA alternating with asymptomatic intervals of apparent recovery. This condition is caused by SPIROCHETES of the genus BORRELIA. It is transmitted by the BITES of either the body louse (PEDICULUS humanus corporis), for which humans are the reservoir, or by soft ticks of the genus ORNITHODOROS, for which rodents and other animals are the principal reservoirs.

Rheumatic Fever - A febrile disease occurring as a delayed sequela of infections with STREPTOCOCCUS PYOGENES. It is characterized by multiple focal inflammatory lesions of the connective tissue structures, such as the heart, blood vessels, and joints (POLYARTHRITIS) and brain, and by the presence of ASCHOFF BODIES in the myocardium and skin.

Rhinitis, Allergic, Seasonal - Allergic rhinitis that occurs at the same time every year. It is characterized by acute CONJUNCTIVITIS with lacrimation and ITCHING, and regarded as an allergic condition triggered by specific ALLERGENS.

Rickettsia - A genus of gram-negative, aerobic, rod-shaped bacteria often surrounded by a protein microcapsular layer and slime layer. The natural cycle of its organisms generally involves a vertebrate and an invertebrate host. Species of the genus are the etiological agents of human diseases, such as typhus.

Rickettsia conorii - A species of gram-negative, aerobic bacteria that is the etiologic agent of BOUTONNEUSE FEVER. It resembles RICKETTSIA RICKETTSII but is antigenically distinct and less virulent for animals and man. (From Bergey's Manual of Systematic Bacteriology, vol 1)

Rickettsia prowazekii - A species of gram-negative, aerobic bacteria that is the etiologic agent of epidemic typhus fever acquired through contact with lice (TYPHUS, EPIDEMIC LOUSE-BORNE) as well as Brill's disease.

Rickettsia rickettsii - A species of gram-negative, aerobic bacteria that is the etiologic agent of ROCKY MOUNTAIN SPOTTED FEVER. Its cells are slightly smaller and more uniform in size than those of RICKETTSIA PROWAZEKII.

Rift Valley Fever - An acute infection caused by the RIFT VALLEY FEVER VIRUS, an RNA arthropod-borne virus, affecting domestic animals and humans. In animals, symptoms include HEPATITIS; abortion (ABORTION, VETERINARY); and DEATH. In humans, symptoms range from those of a flu-like disease to hemorrhagic fever, ENCEPHALITIS, or BLINDNESS.

RNA - A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)

Rocky Mountain Spotted Fever - An acute febrile illness caused by RICKETTSIA RICKETTSII. It is transmitted to humans by bites of infected ticks and occurs only in North and South America. Characteristics include a sudden onset with headache and chills and fever lasting about two to three weeks. A cutaneous rash commonly appears on the extremities and trunk about the fourth day of illness.

Scarlet Fever - Infection with group A streptococci that is characterized by tonsillitis and pharyngitis. An erythematous rash is commonly present.

Schistosomiasis - Infection with flukes (trematodes) of the genus SCHISTOSOMA. Three species produce the most frequent clinical diseases: SCHISTOSOMA HAEMATOBIUM (endemic in Africa and the Middle East), SCHISTOSOMA MANSONI (in Egypt, northern and southern Africa, some West Indies islands, northern 2/3 of South America), and SCHISTOSOMA JAPONICUM (in Japan, China, the Philippines, Celebes, Thailand, Laos). S. mansoni is often seen in Puerto Ricans living in the United States.

Scrub Typhus - An acute infectious disease caused by ORIENTIA TSUTSUGAMUSHI. It is limited to eastern and southeastern Asia, India, northern Australia, and the adjacent islands. Characteristics include the formation of a primary cutaneous lesion at the site of the bite of an infected mite, fever lasting about two weeks, and a maculopapular rash.

Seizures, Febrile - Seizures that occur during a febrile episode. It is a common condition, affecting 2-5% of children aged 3 months to five years. An autosomal dominant pattern of inheritance has been identified in some families. The majority are simple febrile seizures (generally defined as generalized onset, single seizures with a duration of less than 30 minutes). Complex febrile seizures are characterized by focal onset, duration greater than 30 minutes, and/or more than one seizure in a 24 hour period. The likelihood of developing epilepsy (i.e., a nonfebrile seizure disorder) following simple febrile seizures is low. Complex febrile seizures are associated with a moderately increased incidence of epilepsy. (From Menkes, Textbook of Child Neurology, 5th ed, p784)

Severe Dengue - A virulent form of dengue characterized by THROMBOCYTOPENIA and an increase in vascular permeability (grades I and II) and distinguished by a positive pain test (e.g., TOURNIQUET PAIN TEST). When accompanied by SHOCK (grades III and IV), it is called dengue shock syndrome.

Spotted Fever Group Rickettsiosis - A group of arthropod-borne diseases caused by spotted fever bio-group members of RICKETTSIA. They are characterized by fever, headache, and petechial (spotted) rash.

Tanacetum parthenium - An aromatic perennial plant species that has been used to treat migraines, arthritis, and as a febrifuge. It contains TANNINS, volatile oils (OILS, ESSENTIAL), and sesquiterpene lactones, especially parthenolide.

Theileria - A genus of tick-borne protozoa parasitic in the lymphocytes, erythrocytes, and endothelial cells of mammals. Its organisms multiply asexually and then invade erythrocytes, where they undergo no further reproduction until ingested by a transmitting tick.

Theileriasis - Infection of cattle, sheep, or goats with protozoa of the genus THEILERIA. This infection results in an acute or chronic febrile condition.

Trench Fever - An intermittent fever characterized by intervals of chills, fever, and splenomegaly each of which may last as long as 40 hours. It is caused by BARTONELLA QUINTANA and transmitted by the human louse.

Typhoid Fever - An acute systemic febrile infection caused by SALMONELLA TYPHI, a serotype of SALMONELLA ENTERICA.

Typhus, Epidemic Louse-Borne - The classic form of typhus, caused by RICKETTSIA PROWAZEKII, which is transmitted from man to man by the louse Pediculus humanus corporis. This disease is characterized by the sudden onset of intense headache, malaise, and generalized myalgia followed by the formation of a macular skin eruption and vascular and neurologic disturbances.

Uveoparotid Fever - A manifestation of sarcoidosis marked by chronic inflammation of the parotid gland and the uvea.

Yellow Fever - An acute infectious disease primarily of the tropics, caused by a virus and transmitted to man by mosquitoes of the genera Aedes and Haemagogus. The severe form is characterized by fever, HEMOLYTIC JAUNDICE, and renal damage.

Yellow Fever Vaccine - Vaccine used to prevent YELLOW FEVER. It consists of a live attenuated 17D strain of the YELLOW FEVER VIRUS.

Zika Virus Infection - A viral disease transmitted by the bite of AEDES mosquitoes infected with ZIKA VIRUS. Its mild DENGUE-like symptoms include fever, rash, headaches and ARTHRALGIA. The viral infection during pregnancy, in rare cases, is associated with congenital brain and ocular abnormalities, called Congenital Zika Syndrome, including MICROCEPHALY and may also lead to GUILLAIN-BARRE SYNDROME.

Instructional Notations

Type 1 Excludes

A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.

• chills without fever R68.83
• febrile convulsions R56.0
• fever of unknown origin during labor O75.2
• fever of unknown origin in newborn P81.9
• hypothermia due to illness R68.0
• malignant hyperthermia due to anesthesia T88.3
• puerperal pyrexia NOS O86.4