A fever is the body’s natural response to infection and is a higher-than-normal body temperature. A low-grade fever may not be a cause for concern, but a temperature of 102°F and above should be treated. 

• For adults, a temperature higher than 100.4°F is said to be a condition of having a fever.
• For kids, a temperature higher than 100.4°F (measured rectally); 99.5°F (measured orally); or 99°F (measured under the arm) indicates the presence of fever.

What Causes Fever?

The response to diseases by your immune system causes your body temperature to rise. This condition prompts complex processes producing more heat and restricting heat loss.

Fever or elevated body temperature is caused by:

• A viral infection
• A bacterial infection
• Heat exhaustion
• Certain inflammatory conditions such as rheumatoid arthritis
• A cancerous (malignant) tumour
• Some medications like antibiotics and drugs used to treat high blood pressure or seizures
• Some immunizes like diphtheria, tetanus and acellular pertussis (DTaP), pneumococcal or COVID vaccine

Types Of Fevers

Dengue fever

This kind of fever is classified as a mosquito-borne viral disease occurring in tropical and subtropical areas. Getting infected with the virus a second time causes a significantly greater risk of developing severe disease.

Symptoms

• High fever
• Headache
• Rash
• Muscle and joint pain
• Vomiting
• Pain behind the eyes
• Swollen glands
• In severe cases there is serious bleeding which can be life-threatening.

Leptospirosis Fever

This is a bacterial disease that affects humans and animals and is caused by bacteria of the genus Leptospira. In certain cases, some infected persons may have no symptoms at all.

If not treated, Leptospirosis can lead to kidney damage, meningitis, liver failure, respiratory distress, and even death.

Symptoms                  

• High fever
• Headache
• Chills
• Muscle aches
• Vomiting
• Jaundice (yellow skin and eyes)
• Red eyes
• Abdominal pain
• Diarrhea
• Rash

Malaria

 Malaria is caused by a parasite that spreads to humans through the bites of infected mosquitoes. People with malaria feel very sick with a high fever and shaking chills.

Though this disease is uncommon in temperate climates, malaria is still common in tropical and subtropical countries.

For children who live in countries with high numbers of malaria cases, The World Health Organization has recommended a malaria vaccine.

Symptoms

• Fever
• Chills
• General feeling of discomfort
• Headache
• Nausea and vomiting
• Diarrhea
• Abdominal pain
• Muscle or joint pain
• Fatigue
• Rapid breathing
• Rapid heart rate
• Cough

Typhoid

Typhoid fever is caused by Salmonella typhi bacteria and is rare in developed countries. But it is still a serious health threat in the developing world, especially among children.

Contaminated water and food or close contact with an infected person can cause typhoid fever.

Symptoms

• High fever
• Headache
• Stomach pain
• Constipation or diarrhea

Most people feel better a few days after they start antibiotic treatment, but a small number of them may die due to complications. Vaccines are usually reserved for those who may be exposed to the disease or who are traveling to areas where typhoid fever is common.

Rickettsia

Rickettsial infections (rickettsioses) are associated with the patient having been bitten by an ectoparasite such as a mite, louse, flea, or tick. Rickettsioses in humans are caused by several related genera of bacteria like Rickettsia species, Orientia tsutsugamushi and O chuto, Anaplasma species, Ehrlichia species, and Neoehrlichia species.

The genus Rickettsia is divided into the spotted fever group (SFG) and the typhus group (TG). In the former type, the patients experience fever and spots.

Symptoms

• fever >38°C
• Rash
• Eschar
• lymphadenopathy associated with eschar

Chikungunya

This is a form of viral infection transmitted by mosquitoes. Chikungunya is found worldwide, particularly in Africa, Asia, and India. Symptoms normally appear within a week of infection.

Symptoms

• Fever and joint pain
• Muscle pain
• Headache
• Fatigue
• Rash may also occur

Most people feel better within a week after the virus runs its course.

Pyrexia of Unknown Origin

The natural immune response of the body against disease-causing organisms and severe illnesses causes Pyrexia. The temperature level is usually measured from oral or axillary regions and rarely from the rectal area. The rectal area shows accurate readings as it records the temperature of the core areas.

The causes of pyrexia may be infectious or non-infectious. The common reasons for pyrexia are listed here:

Infectious Causes

• Lower respiratory tract infections like bronchitis
• A bacterial lung infection called tuberculosis
• Complicated urinary tract infections
• Bone infections like Osteomyelitis
• A bacterial infection of the cardiac tissue called endocarditis
• Viral infections like HIV (Human-Immunodeficiency syndrome) and Cytomegalovirus

Non-infectious Causes

• Neurological conditions like brain fever or haemorrhages
• Malignant conditions like Leukaemia and renal cell carcinoma
• Reactions to drugs
• Bowel or bladder-related problems
• Reactions to blood transfusion

Symptoms

• Shivering or chills
• Headache
• Generalised body pains and weakness
• Irritability
• Dehydration
• Loss of appetite
• Joint pains
• Sweating

 Diagnosis for the types of Fevers mentioned above

Fever is usually a sign of infection and taking the associated tests or a fever panel can help to identify the presence of infection and allows the doctor to suggest correct medication and treatment.

Major Tests for Fevers Includes:

•  Dengue Fever - Dengue NS-1 antigen (first 5 days) and Dengue IgM and IgG and Complete Blood Count (CBC)
• Leptospirosis Fever- Leptospiral antibody IgM and IgG and Complete Blood Count (CBC)
• Malaria -Rapid malarial parasite test (RMT), malarial parasite slide test, malaria antigen test, and Complete Blood Count (CBC)
• Typhoid - Typhidot Test, Widal Test, and Complete Blood Count (CBC)
• Rickettsia - Scrub typhus IgM, Weil Felix test, and Complete Blood Count (CBC)
• Chikungunya – Chikungunya IgM Test and Complete Blood Count (CBC)
• Pyrexia of Unknown Origin – Tests for Dengue, Leptospirosis, Malaria, Typhoid, Rickettsia, Chikungunya, HIV 1 & 2 antibodies, Tuberculosis, and Complete Blood Count (CBC)

 Conclusion

Fever is a general sign that something is wrong with the body. We usually tend to take it lightly or do self-medication which is not the right way to deal with it. Knowing the underlying cause of fever is necessary not only for its treatment but also to avoid complications. Always consult your physician and take the prescribed tests without fail to determine and commence the right medication.