In recent weeks, there has been an increase in the number of cases of chikungunya viral (CHIKV) infections in Sri Lanka.
What is the CHIKV?
CHIKV – pronounced chik‐n‐gunya, with the accent on the first syllable – is a mosquito-borne viral disease caused by the CHIKV. This is a ribonucleic acid (RNA) virus in the Alphavirus genus and Togaviridae family. The name CHIKV is derived from the Makonde (or Kimakonde) word, meaning ‘that which bends up’. This is in reference to the stooped posture that develops from the arthritic (a disorder that affects the joints) symptoms of the disease.
When was this condition first described and where does it occur?
The CHIKV disease (CHIKVD) was first described in Tanzania in 1952-1953. Since then, outbreaks have been reported from the Americas, Africa and many parts of Asia. In 1958, the virus was first isolated in Asia, from Bangkok, Thailand. During the first three months of this year, approximately 80,000 cases of CHIKVD and fifty CHIKVD-related deaths have been reported from the Americas, Africa and Asia. Most of the cases were from the Americas, whilst cases have also been reported from Pakistan, Sri Lanka, and Senegal. Most of the CHIKVD-related deaths have been in Brazil.
How is the CHIKV transmitted?
The CHIKV is transmitted by infected female mosquitoes, most commonly Aedes aegypti and Aedes albopictus. These mosquitoes also transmit the Dengue and Zika viruses and are widely distributed in several South and South Asian countries. They bite primarily during daylight hours and the Aedes aegypti feeds both indoors and outdoors. They lay eggs in containers with standing water.
What clinical features are found in the CHIKVD?
In some, the infection may be asymptomatic, whilst others develop a range of symptoms. Symptoms typically occur four-eight days (range 2-12 days) after the bite of an infected mosquito. These include an abrupt onset of fever, frequently accompanied by severe joint pain. The joint pain is often debilitating and usually lasts for a few days. In some, they become more prolonged, lasting for weeks, months or even years. Other features include joint swelling, muscle pain, headache, nausea, fatigue, rash, sore mouth or mouth ulcers. Many of these symptoms overlap with other infections, including the Dengue and Zika virus infections.
CHIK can cause a range of complications including chronic arthritis (long-lasting joint inflammation and pain), encephalitis (inflammation of the active tissues of the brain), encephalopathy (a change in how the brain functions), myelitis (inflammation of the spinal cord) and a variety of skin, eye, cardiac and liver problems. Newborns, those older than 65 years, and people with diabetes, hypertension, heart disease or immune-related disorders are at risk for more severe complications. Persistent joint pain has been found to be associated with elevated levels of some immune chemicals such as Interleukin Six (IL-6) and Granulocyte-macrophage colony-stimulating factor (GM-CSF).
How is the CHIKV diagnosed?
During the first week of illness, the reverse transcriptase–polymerase chain reaction (RT-PCR) test for CHIKV may be done on a blood sample. Immunoglobulin M (IgM) antibody tests to assess the immune response to the CHIKV infection may be used, typically at or after the first week of infection. These antibodies may persist for about two months, post-infection.
What treatment is available for the CHIKVD?
Currently, there is no specific antiviral therapy for CHIKVD. However, a number of treatment options are under investigation. Symptomatic treatment includes adequate amounts of rest, drinking sufficient amounts of fluid, and the use of analgesics and antipyretics (medicines to reduce pain and fever). Although non-steroidal anti-inflammatory drugs can be used to help the fever and joint pain, in dengue-endemic countries such as Sri Lanka, paracetamol (acetaminophen) is the preferred first treatment for such symptoms. This is until Dengue has been ruled out, so as to reduce the risk of haemorrhage, if the diagnosis is actually Dengue. Patients with suspected CHIKVD should be managed as Dengue until Dengue has been ruled out. For patients with persistent joint pain related to CHIKVD, the use of non-steroidal anti-inflammatory drugs, corticosteroids including topical preparations, and physical therapy might help reduce the intensity of the symptoms.
How is the CHIKV prevented and controlled?
The avoidance of mosquito bites is the best protection against CHIKV infections. To prevent further transmission, those suspected of having a CHIKV infection should avoid getting bitten by a mosquito during the first week of illness. The reduction of mosquito breeding sites (through emptying and cleaning containers that contain water on a weekly basis, the disposing of waste, and supporting local mosquito control programmes) is important.
According to the World Health Organisation, during outbreaks, insecticides may be sprayed to kill flying adult mosquitoes, applied to surfaces in and around containers where the mosquitoes land, and used to treat water in containers to kill the immature mosquito larvae. People living in or visiting areas with CHIKV transmission are advised to wear clothing that minimises skin exposure to the day-biting mosquitoes. Window and door screens should be used to prevent mosquitoes from entering homes. Repellents (containing N,N-diethyl-meta-toluamide/diethyltoluamide [DEET], Ethyl butylacetylaminopropionate [IR3535] or Icaridin) can be applied to exposed skin or to clothing. For those who may sleep during the daytime (young children, sick patients or older people), insecticide-treated mosquito nets should be used.
The United States Food and Drug Administration approved a vaccine for CHIK called IXCHIQ, in late 2023. It was approved for those older than 18 years, with an increased risk of exposure to the virus. The vaccine is also authorised in the European Union, but access to the vaccine remains very limited in CHIK endemic areas. Those who are infected with CHIK are likely to be protected from future infections.
Conclusions
A basic knowledge of the clinical features, diagnosis, treatment and prevention of CHIKV infections by both the general public and healthcare staff, would help achieve the optimal management of CHIV-infected patients.
(The writer is a Consultant in Clinical Immunology and Allergy)
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The views and opinions expressed in this article are those of the author, and do not necessarily reflect those of this publication