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WHO experts are warning against the outbreak of chikungunya
On 22 February, WHO experts warned that the mosquito-borne disease, chikungunya fever, is spreading globally. Transmission of the virus has already been detected in 119 countries and territories, putting about 5.5 million people at risk of infection. Diana Alvarez, head of the WHO's insect-borne virus team, said the virus could lead to widespread outbreaks, putting pressure on health systems. Outbreaks have already been reported this year on the French island of Réunion, in India and Bangladesh, and in European countries, with both imported and locally transmitted cases. Chikungunya fever is mainly transmitted by Aedes aegypti mosquitoes and can lead to high fever and severe joint pain. In severe cases, it can be fatal. The WHO is assisting Member States to strengthen surveillance, prevention, and control measures.
Clinical symptoms and diagnosis
The most common symptoms of a chikungunya infection are fever and arthralgia. Other symptoms may include headache, myalgia, nausea and rash. Approximately half of patients with laboratory-confirmed symptomatic chikungunya fever develop chronic disability following infection, with 4% requiring hospitalization. In recent decades, as attention has increased regarding arboviruses, less common manifestations of atypical chikungunya infections have also been reported in case and surveillance reports. These include neurologic symptoms such as Guillain-Barré syndrome, encephalitis, seizures, confusion and stroke, which may be associated with cardiopulmonary failure, digestive and liver disease, kidney disease and muscle damage. As the clinical features of chikungunya fever are similar to those of other mosquito-borne diseases, diagnosis based on clinical presentation alone is challenging. Current diagnostic tools include virus isolation, polymerase chain reaction (PCR) and antibody detection tests. Differential diagnoses include other infectious diseases presenting with arthralgia, myalgia and fever, such as leptospirosis, Zika virus disease, dengue fever, malaria, meningitis and rheumatic fever.
Detection Methods
There are three common testing methods: serological testing, nucleic acid testing, and virus isolation. In general, virus isolation and nucleic acid testing should be performed on serum within one week of the onset of the disease. Serum taken four days after the onset of the disease should be used for IgM antibody testing and serum taken one week after the onset of the disease should be used for IgG antibody testing.
Serological tests
1．Specific IgM assay
The methods include capture ELISA (MacELISA), indirect ELISA, immunofluorescence and immunochromatography.
2．Specific IgG assay
The methods include indirect ELISA, immunofluorescence and immunochromatography.
3．Significance
(1) A positive IgM result indicates that the patient has a recent CHIKV infection and can be used for the early diagnosis of chikungunya fever.
(2) A positive IgG result indicates a previous CHIKV infection. The diagnosis is confirmed by a fourfold or greater increase in serum antibody titers in the recovery phase compared with the acute phase.
Pathogenetic tests
1. Chikungunya virus nucleic acid test
Viral nucleic acids can usually be detected in most patients' serum within seven days of the onset of symptoms. Frozen Aedes aegypti specimens can also be tested for the presence of the chikungunya virus. Methods such as RT-PCR and real-time RT-PCR can be used for nucleic acid amplification and detection.
2. virus isolation and characterization
Vero and C6/36 are sensitive cell lines that are commonly used for virus isolation. Isolates can be identified using immunofluorescence or nucleic acid assays.
3. Significance
A diagnosis of chikungunya virus infection is confirmed by isolating the virus in serum samples from the patient and/or detecting viral nucleic acid.
DIAGREAT Chikungunya Virus lgG/lgM Rapid Test Kit (Colloidal Gold Assay)
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