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(place here) Chikungunya

Refs: GOV.UK ====== CDC ====== Mayo ====== National Foundation for Infectious Diseases (NFID) ===== Royal Vet College (Vairo et al) ====== Burt et al ====== WHO Factsheet 2025 ===== LSHTM: Chikungunya – what you need to know

Diagnosing chikungunya can be difficult because its symptoms, such as sudden fever and joint pain, closely resemble other mosquito-borne illnesses like dengue fever and malaria. Chikungunya should be suspected if a patient with these symptoms either lives in an area where the virus is endemic, or if f they have recently traveled to such an area. The Aedes mosquitoes which carry chikungunya virus can also carry other viruses such as dengue, zika, and yellow fever.

During the first week of illness, when virus is present in the bloodstream, it is possible to detect viral RNA in a blood sample using techniques such as reverse transcription-polymerase chain reaction (RT-PCR) or viral culture. After this time, the body develops antibodies and the virus is eliminated from the bloodstream. Antibodies in blood serum persist for between 3 and 12 months; they can be detected for up to a year after infection using enzyme-linked immunosorbent assay (ELISA) or indirect fluorescent antibody (IFA). All of these techniques are time consuming and costly, requiring sophisticated laboratory equipment which may not be available in resource poor settings.

Differential diagnosis

The Aedes mosquitoes which carry chikungunya virus can also carry other viruses such as dengue, zika, and yellow fever. Other infections which should be considered include malaria, leptospirosis, measles, mononucleosis and African tick bite fever, which are often endemic in the same areas and can have similar symptoms. It is possible for a patient to be infected by more than one virus simultaneously.

Diagnostic process

Patient history

Symptoms

Tests

Source material & AI text

Existing text

Chikungunya is diagnosed on the basis of clinical, epidemiological, and laboratory criteria. Clinically, acute onset of high fever and severe joint pain would lead to suspicion of chikungunya. Epidemiological criteria consist of whether the individual has traveled to or spent time in an area in which chikungunya is present within the last twelve days (i.e., the potential incubation period). Laboratory criteria include a decreased lymphocyte count consistent with viremia. However a definitive laboratory diagnosis can be accomplished through viral isolation, RT-PCR, or serological diagnosis.

The differential diagnosis may include other mosquito-borne diseases, such as dengue or malaria, or other infections such as influenza. Chronic recurrent polyarthralgia occurs in at least 20% of chikungunya patients one year after infection, whereas such symptoms are uncommon in dengue.

Virus isolation provides the most definitive diagnosis, but takes one to two weeks for completion and must be carried out in biosafety level III laboratories. The technique involves exposing specific cell lines to samples from whole blood and identifying chikungunya virus-specific responses. RT-PCR using nested primer pairs is used to amplify several chikungunya-specific genes from whole blood, generating thousands to millions of copies of the genes to identify them. RT-PCR can also quantify the viral load in the blood. Using RT-PCR, diagnostic results can be available in one to two days. For rapid identification and genotyping of the chikungunya virus, a method combining RT-PCR with restriction fragment length polymorphism (RFLP) analysis can be used. It is based on amplifying a specific 648 bp fragment of the nsP2 gene, encoding nonstructural protein 2. The unique pattern of restriction sites for the endonucleases PspEI, PvuII, and DraI within this fragment allows for the discrimination of the four major virus genotypes.

Serological diagnosis requires a larger amount of blood than the other methods and uses an ELISA assay to measure chikungunya-specific immunoglobulin M levels in the blood serum. One advantage offered by serological diagnosis is that serum IgM is detectable from 5 days to months after the onset of symptoms, but drawbacks are that results may require two to three days, and false positives can occur with infection due to other related viruses, such as o'nyong'nyong virus and Semliki Forest virus.

Presently, there is no specific way to test for chronic signs and symptoms associated with chikungunya fever although nonspecific laboratory findings such as C reactive protein and elevated cytokines can correlate with disease activity.

Google: Diagnosis of chik

WHO Factsheet 2025

Chikungunya is diagnosed through a combination of clinical symptoms (like sudden fever and joint pain), patient history (including travel to endemic areas), and laboratory tests. For early diagnosis, molecular tests like RT-PCR can detect the virus's RNA in the blood during the first week of illness. As the illness progresses, serological tests can detect specific IgM antibodies, which become detectable around 4–7 days after symptom onset.  

Early diagnosis (first week of illness)

• Clinical suspicion: Doctors will suspect chikungunya if a patient presents with a sudden onset of high fever and severe joint pain, especially if they have traveled to or live in an area where the virus is present.
• Molecular tests: During the first week, the virus itself can be detected by testing for its RNA in a blood sample using a reverse transcriptase–polymerase chain reaction (RT-PCR) test.

Later diagnosis (after the first week)

• Serological tests: Once the acute phase has passed, the body's immune response can be checked for antibodies.
• IgM antibodies: These antibodies are typically detectable from around day 4–7 after the illness begins and can persist for several months.
• IgG antibodies: These appear after IgM and can persist for a longer period, sometimes for years.
• Viral isolation: It is also possible to isolate the virus from blood samples collected early in the illness, though this is less common than other testing methods.

Important considerations

• Dengue and Zika: Because chikungunya, dengue, and Zika are all transmitted by the same mosquitoes and can present with similar symptoms, it is crucial to rule out other infections.
• Differential diagnosis: A doctor will consider these other mosquito-borne illnesses in their diagnostic evaluation.

Laboratory Diagnosis of Chikungunya Virus Infections (johnson et al, 2016)

Detection of chikungunya virus (CHIKV) or viral RNA is the primary laboratory test used to diagnose infection in serum collected <6 days after onset of illness. ..... Detection of CHIKV-specific immunoglobulin M (IgM) antibody becomes a sensitive test for samples collected approximately >5 days of illness.

CDC

Recommended tests

During the first 8 days of illness, chikungunya viral RNA can often be identified in serum using reverse transcription-polymerase chain reaction (RT-PCR). Viral culture may detect virus in the first 3 days of illness; however, chikungunya virus should be handled under biosafety level (BSL) 3 conditions. Chikungunya virus antibodies normally develop toward the end of the first week of illness. Therefore, to definitively rule out the diagnosis, convalescent-phase samples should be obtained from patients whose acute-phase samples test negative.

Google: Differential diagnosis

Statpearls

The differential diagnosis of chikungunya includes other arboviruses like dengue and Zika, as well as other infections such as malaria, leptospirosis, measles, and mononucleosis. The similarity in symptoms like fever, rash, and joint/muscle pain makes it challenging to distinguish from these conditions, necessitating laboratory confirmation. In cases of chronic arthritis, autoimmune conditions like rheumatoid arthritis and spondyloarthropathy should also be considered.

Google: Difficulty

LSHTM:

Yes, diagnosing chikungunya can be difficult because its symptoms, such as sudden fever and joint pain, closely mimic other mosquito-borne illnesses like dengue fever and malaria. A definitive diagnosis requires laboratory confirmation, typically through blood tests like RT-PCR or serologic tests that detect antibodies (IgM or IgG), as symptoms alone are often not specific enough.

Reasons for diagnostic difficulty

• Symptom overlap: The primary symptoms of chikungunya, including fever, joint pain, muscle pain, headache, and rash, are very similar to other diseases that can occur in the same geographic regions.
• Concurrent infections: In many areas, chikungunya co-circulates with other arboviruses like dengue and Zika, making it even more challenging to distinguish based on symptoms alone.
• Nonspecific symptoms: Many of the initial symptoms are non-specific, making it easy to misdiagnose the infection.

Keep for future reference

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Temperature conversion

40–41 °C (104–106 °F)

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H5N1 deaths (transcluded from Human mortality from H5N1)

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Between 2003 and February 2025, the World Health Organization has recorded 972 cases of confirmed H5N1 influenza, leading to 468 deaths. The true fatality rate may be lower because some cases with mild symptoms may not have been identified as H5N1.