Chikungunya Fever

• Chikungunya fever occurs in both sporadic outbreaks and large epidemics in Africa, the Indian subcontinent and Southeast Asia, particularly the Philippines, Thailand, Cambodia, Vietnam, Mauritius and Sri Lanka.
• Of the indigenous population it appears to affect mostly those between about 5 and 9 years old.
• It is said to affect thousands of people throughout the world every year, but the WHO do not offer figures.
• The disease is rarely imported to other countries by travellers returning from endemic areas.^1,2

Risk factors

Risk is highest in the rainy season when mosquitoes are at their greatest numbers.

The illness characteristically begins with rapid onset of joint pains and may or may not be accompanied by the following: muscle pain, high fever, conjunctivitis and a rash.

• Incubation period is 2 to 4 days.
• There is sudden onset of fever and with it a severe, crippling migrating, polyarticular arthritis. This is due to the virus invading and causing inflammation of the cartilage.³
• Between the 2nd and 5th day of illness there is a macular or maculopapular rash, mostly on the trunk and limbs.
• There may be conjunctivitis and minor bleeding in the skin and eye.
• Most patients recover in a few days and death is a rarity. Arthritis may persist for rather longer, even several months or years.

• There was a massive outbreak in the French island of La Reunion in the Indian Ocean, in 2005 and 2006, which also affected neighbouring islands, including Mauritius.⁴
• The French authorities estimate around 150,000 cases have occurred.
• Almost a quarter of patients had haemorrhagic symptoms, such as bleeding from the nose or gums.
• Since the beginning of the outbreak in La Reunion, 181 deaths have been reported, directly or indirectly related to Chikungunya, mostly among elderly patients with other medical conditions.
• Whether the deaths are directly related to Chikungunya is still under investigation. There were 154 patients (older than 10 days of age) who presented with a severe form of Chikungunya, 120 of whom are confirmed.
• The signs of severity include meningo-encephalitis, cardiovascular decompensation, or respiratory failure.
• In infants less than 10 days old, 44 infections have been reported, 37 of which were confirmed. Twelve of these newborns presented with meningo-encephalitis. Transplacental transmission has been suggested.
• This outbreak appears to be unusually virulent and deaths are mostly amongst those with other medical conditions.⁵

Serological testing can be used to confirm the diagnosis. More recently indirect immunofluorescence has become available.⁶ Extreme care should be taken when obtaining blood samples and handling specimens.

The picture may be confused with the various viral haemorrhagic fevers or malaria.

Chikungunya is very similar in presentation to Dengue. The main differences are:

• In classical Dengue there is no hepatomegaly whilst that is present in Chikungunya and haemorrhagic Dengue.
• In haemorrhagic Dengue there is also a confluent petechial rash.

• Fever is marked and especially in a hot environment, plenty of fluid should be drunk.
• Paracetamol and ibuprofen may help relieve pyrexia and pain.
• Sometimes chloroquine is used for persistent arthritis. This is based on a pilot study in 1984 that has not been repeated since.⁷

The relationship between malaria, glandular fever and Burkitt's lymphoma is well known, but the distribution in Africa may mirror that of Chikungunya fever too.^8,9

The illness appears to be less severe in children. The majority of patients will recover but some may be left with chronic joint pains which may last several years.¹⁰ Chikungunya virus does not cause death directly but in the presence of other co-morbidities it may contribute to a fatal outcome.

Epidemics have been associated with poor control of mosquitoes.¹¹ Prevention requires the use of insect repellants and elimination of breeding places for mosquitoes e.g. stagnant water.