Prolonged fever and fever after travel

What is a prolonged fever?

The NHS counts a temperature of 38 degrees or higher as a fever, and says that sometimes a person has a fever even with a thermometer reading below 38, and feels shivery, hot, or unusually cold. Most fevers are a sign of simple infections and get better on their own.

When a fever lasts for weeks and the first round of checks does not explain it, the AAFP calls it “fever of unknown origin”. This source’s accepted definition is a recorded temperature of 38.3 degrees or higher on several occasions. The causes fall into four groups: infections, cancers, non-infectious inflammatory diseases, and a miscellaneous group that includes drug fever and blood clots in veins. So a long fever is not always infectious, and part of the doctor’s work is sorting out these groups.

Fever after travel

After a return from travel, the doctor first rules out malaria. The CDC Yellow Book says malaria must be ruled out in every feverish patient who has come back from an endemic area, and treats falciparum malaria as a medical emergency. The same source says malaria is the most common life-threatening tropical illness with fever in returning travellers. Test results should be available urgently, within hours.

Timing matters too. The NHS says symptoms usually appear 7 to 18 days after a bite, but sometimes months later and rarely years later. Both sources treat the past year as the important window. According to the Yellow Book, most ill travellers seek care within a month of returning.

Malaria is not the only cause. The same source names dengue as the most common cause of fever in patients seen after travel to Latin America or Asia, and counts typhoid (enteric fever) among the important travel-related illnesses. A fever lasting more than two weeks has another list that includes brucellosis and tuberculosis, and the doctor weighs this list against your history. The Yellow Book notes that in at least a quarter of returning travellers with fever, no cause is identified.

Who should be seen?

• A fever that does not improve with home care, or gets worse (NHS).
• A fever of unknown origin that continues for weeks, or comes and goes for no clear reason.
• Anyone who has been to a malaria area (for example south-eastern Iran, Afghanistan, Pakistan, India or Africa) in the past year and now has a fever, chills, or feels hot and cold. In this case do not wait for a routine appointment; go to a hospital emergency department or a health centre the same day and say that you need a malaria test.
• A fever with weight loss, night sweats, or a cough lasting more than three weeks (the NHS signs for tuberculosis).
• A fever in someone taking medicine that suppresses immunity, who has had an organ transplant, or who has HIV.

How is it investigated?

For the history, the AAFP lists: travel, occupation, where you live, recent medicines, contact with animals or sick people, and smoking and alcohol use. For a traveller, the Yellow Book asks for more detail: destinations and dates, where you stayed, what you drank and ate, insect or animal bites, swimming in fresh water, vaccines, and malaria prevention medicine. Before the visit, prepare the fever log and the first-visit checklist.

The AAFP’s first-line tests are a blood count, urine test and culture, three sets of blood cultures, a chest X-ray, inflammation markers, and serology and tuberculosis tests. Depending on the findings, an ultrasound, CT scan or echocardiogram is added. For malaria, the Yellow Book recommends a blood test examined under the microscope, and if the result is negative but suspicion remains, repeating it two or three times over 24 to 48 hours. Proper sampling is covered in the samples and cultures guide.

What does treatment look like in general?

Treatment follows the cause, and for that reason the doctor is usually in no hurry to give an antibiotic until the cause is clear. The AAFP says guesswork antibiotics are not proven for fever of unknown origin and are set aside only for a patient with a very low white blood cell count, weakened immunity, or serious illness. The Yellow Book also says treating malaria on suspicion alone is not recommended except in rare cases.

Malaria is treated with antimalarial medicines. The CDC says the type of medicine and the length of treatment depend on the type of malaria, where it was caught, severity, age and pregnancy, and that starting treatment early often prevents severe illness and death. The NHS also says some patients need to be admitted to hospital. Local illnesses such as brucellosis and tuberculosis are covered on the endemic infections page.

What can you do yourself?

• The NHS advises resting, drinking plenty of fluids, and staying home until your temperature is back to normal. The aim is light, pale urine. Staying home means not going to work or mixing with other people, not putting off seeing a doctor.
• Write down your temperature with the time, and any medicines you have taken.
• Do not use leftover antibiotics or other people’s medicine. This hides the cause and may change the culture result.
• Tell the doctor about every medicine, including herbal and over-the-counter ones. Drug fever is a known cause.
• If you travelled with others and malaria is possible, the NHS says to let your travel companions know so they can be checked.

When to act urgently

Call 115 (Iran’s emergency number) right now for: confusion, fast breathing, a stiff neck with a severe headache, a rash that does not fade under pressure, bluish or pale skin, a seizure, or a condition that worsens like sepsis. The full list is in the urgent signs.

Same-day care: a fever or chills after travel to a malaria area in the past year. The NHS says that if you are still travelling, do not wait until you get home. Tell the doctor or health centre where you have been. A fever in someone with weakened immunity cannot wait until tomorrow: contact your doctor at once, and if you cannot reach them, go to a hospital emergency department.

This page is for information only and does not replace an examination.