The world's first vaccine for Chikungunya infection will arrive in late summer 2024, following the go-ahead in late May by the European Medicines Agency (EMA) and final approval in late June by the European Commission.
Chikungunya is a self-limiting systemic viral infection caused by the virus of the same name, belonging to the Togaviridae family, transmitted to humans through the bite of infected mosquitoes of the genus Aedes, especially the Aedes aegypti and the Aedes albopictuscommonly known as the 'tiger mosquito'.
It is therefore an arthropod-borne viral disease, which mosquitoes transmit after coming into contact with the virus by biting infected humans or animals, especially monkeys, and thus becoming carriers of the disease throughout their life cycle.
Currently, Chikungunya infection has been identified in over 60 countries in Asia, Africa, Europe and the Americas. In Italy, outbreaks of Chikungunya transmission were identified in 2007 and 2017, sustained by the mosquito Aedes albopictus.
Symptoms
After the bite of an infected mosquito, the onset of Chikungunya infection occurs after 4-8 days, but the incubation period can vary from 2-12 days. At its onset, the disease is characterised by flu-like symptoms, such as high fever, above 39°C, headache, weakness and intense and widespread joint pain, sometimes forcing the patient to assume a folded position. In fact, the term 'chikungunya' in Swahili means 'that which bends' or 'twists'.
Common symptoms include nausea and haemorrhagic-type manifestations such as petechiae, ecchymosis, epistaxis and gum bleeding. After the onset of fever, an itchy rash, typically maculo-papular, involving the trunk and extremities may occur. Neurological, cardiac and gastrointestinal complications may also occur.
In most cases, patients heal spontaneously and completely, however, in some cases joint pain may persist for months or even years.
Sometimes the symptoms in infected persons are rather mild and the infection goes undiagnosed or is confused with other diseases, especially in areas where dengue is present.
Serious complications rarely occur, but in the elderly the disease can be a contributory cause of death.
Ocular complications
Chikungunya virus can cause ocular complications, which include uveitis, retinitis, optic neuritis. In the acute phase of Chikungunya fever, photophobia and retrobulbar pain are often observed, even in the absence of other signs of ocular involvement.
A form of conjunctivitis has also been reported that mimics the characteristics of viral conjunctivitis and resolves spontaneously, usually within a week.
By far the most frequent ocular manifestation is anterior uveitis, in both granulomatous and non-granulomatous forms. Both variants are characterised by the presence of pigmented keratic precipitates and inflammation in the anterior chamber. Uveitis can be bilateral and is often associated with elevated intraocular pressure, which can be managed with anti-glaucomatous eye drops combined with topical steroid medications and cyclopegic agents to treat the inflammation. Inflammation of the anterior segment heals on average within a period of several weeks to a couple of months. Cases of corneal involvement in the form of viral keratitis and lagophthalmos with exposure keratitis have also been reported.
Prevention
Prevention of the disease basically consists of preventing or minimising mosquito bites and following the following general precautions for this purpose:
- Apply mosquito nets to windows and activate air conditioning at least in rooms where people stay
- Wear clothes that do not leave parts of the body uncovered (long-sleeved shirts, long skirts and trousers, etc.) in light colours, as dark colours attract mosquitoes
- Apply repellents to the parts of the body that remain uncovered, bearing in mind that sweat reduces the effect.
It should be noted that some of the mosquito vectors of this disease are active during the day, especially in the morning hours and late afternoon, until sunset.
Treatment
The Chikungunya virus is an RNA virus, unstable over time, for which no antiviral drug is currently available. In the acute phase of the infection, therapy is exclusively aimed at controlling symptoms and involves rest, fluid intake, and the use of analgesics and antipyretics.
Chronic arthritis caused by Chikungunya infection is usually managed with chloroquine phosphate, corticosteroids, anti-rheumatic drugs and also TNF (Tumour Necrosis Factor) blocking agents.
Single-dose vaccine will finally be available in Europe this autumn Ixchiqalready approved in the US and Canada, and can be administered to people over 18 for the prevention of the disease caused by the mosquito-borne Chikungunya virus Aedes.
The EMA's green light is based on the results of phase 3 studies published in The Lancetwhich indicate for Ixchiq a serological response rate of 98.9% at 28 days with a single vaccination. This immune response was maintained for 24 months by the 97% of the study participants and was equally durable in the youngest and oldest participants.
On the subject of "arboviruses" see also
Bilateral chorioretinitis and West Nile virus - Oculista Italiano
- Mahendradas P, Avadhani K, Shetty R. Chikungunya and the eye: a review. J Ophthalmic Inflamm Infect. 2013 Feb 11;3(1):35. doi: 10.1186/1869-5760-3-35. PMID: 23514031; PMCID: PMC3605073.
- World Health Organisation. Guidelines for prevention and control of chikungunya fever. World Health Organization, Regional Office for South-East Asia, New Delhi; 2009.
- Simon F, Javelle E, Oliver M, Leparc-Goffart I, Marimoutou C. Chikungunya virus infection. Curr Infect Dis Rep. 2011;13(3):218-228. doi: 10.1007/s11908-011-0180-1.
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