Chikungunya

Chikungunya has been identified in over 60 countries in Asia, Africa, and recently also in Europe and the Americas. Chikungunya virus often causes large explosive outbreaks with high attack rates, affecting one-third to three-quarters of the population in areas where the virus is circulating between years-long periods of quiescence. International travel is one of the major risk factors for the rapid global spread of the disease.

Persistent severe arthralgias could lead to long-term disability and loss of workdays, resulting in a significant burden on the economy and loss of productivity.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Acute clinical case:

• Clinical criteria: acute onset of fever >38.5°C and severe joint pain; AND Epidemiological criteria: residing or having visited epidemic areas, having reported transmission within 15 days prior to the onset of symptoms; OR
• Laboratory criterion: confirmation by laboratory

WHO case definition source of information: https://www.who.int/docs/default-source/outbreak-toolkit/latest-update---11-october/chik-outbreak-toolbox---25092019.pdf?sfvrsn=209b75c6_2

Significant increase above historical averages in endemic countries. One confirmed case, if there is no known outbreak already under investigation.

• Environments where the Ae. Albopictus mosquito breeds are water-filled sites like tree holes, rock pools, or bamboo stumps, or artificial containers like vehicle tyres or saucers beneath plant pots. Ae. Aegypti on the other hand is more associated with indoor breeding sites such as water storage vessels, concrete water tanks in bathrooms and flower vessels, as well as the same artificial outdoor breeding sites as Ae. Albopictus.
• Increased contact between humans and infected mosquitoes, particularly in urban areas can create epidemics.
• Outbreaks of the disease are of particular concern when they occur in overcrowded settings with inadequate water supply and waste management services that allow the mosquitoes to breed easily.
• Pregnancy in regions where there are chikungunya epidemics.
• Humans travelling to/from endemic/epidemic areas.
• The abundance of Ae. Aegypti and Ae. Albopictus follow seasonal patterns. Increase in temperature and rainfall patterns contribute to the increase and survival of vectors.
• Children and elderly who sleep during the daytime in epidemic areas are at greater risk.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

• Chikungunya affects one-third to three-quarters of the population in areas where the virus is circulating.

• Older people (≥65 years).
• Neonates.
• People with medical conditions such as high blood pressure, diabetes, or heart disease and weakened immune systems.
• Pregnant women.

Chikungunya virus.

Vector: Mosquitoes (Aedes aegypti and Aedes albopictus) are carrying the Chikungunya virus.

Non-human and human primates are likely the main reservoirs of the virus; other potential reservoirs are various vertebrates.

• Vector-borne: From human to human through mosquito bite (Aedes aegypti and Aedes albopictus and some other mosquito vectors in Africa). The mosquitoes usually bite during the daytime (peak biting periods are early in the morning and in the evening at dusk).
• Congenital transmission: Chikungunya virus is transmitted rarely from mother to newborn around the time of birth.
• Vehicle-borne transmission: Blood-borne transmission is possible.

Four to eight days (range 2—12 days).

The virus circulates in the blood of infected humans for several days, at approximately the same time that they have chikungunya fever. Aedes mosquitoes acquire the virus when they feed on an individual during this period.

• 40 to 85 per cent of people develop symptoms after infection:
• Chikungunya is characterized by an abrupt onset of fever frequently accompanied by migratory joint pain, affecting different joints.
• Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash.
• The joint pain is often very debilitating, usually lasts for a few days or may be prolonged to weeks.
• Most patients recover fully, but in some cases joint pain may persist for several months, or even years.
• Serious complications are not common, but in older people, the disease can contribute to the cause of death.
• Haemorrhagic manifestations are uncommon.

Dengue fever, leptospirosis, malaria, meningitis, Zika virus infection, Ebola virus disease and other infections.

• PCR (polymerase chain reaction).
• Virus isolation from blood samples.
• Serological tests, like Enzyme linked immunosorbent assay (ELISA).

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of any treatment should be conducted by health professionals.

Important therapy principles include the following:

• There is no specific antiviral drug treatment for chikungunya.
• Treatment is directed primarily at relieving the symptoms, including joint pain using drugs reducing fever, optimal analgesics and fluids.
• Chikungunya and Dengue have similar clinical presentations and therefore, care should be taken when administering medications such as aspirin or other nonsteroidal anti-inflammatory drugs (e.g. Ibuprofen, Naproxen). These may increase the risk of bleeding if the case is in fact Dengue fever and not Chikungunya.
• There is no commercial chikungunya vaccine.

Recovery from an infection will confer life-long immunity.