Chikungunya

Disease Characteristics

Chikungunya is a mosquito-borne virus infection characterized by symptoms similar to those of dengue fever. Unlike dengue, however, the virus does not lead to the leakage of plasma outside of the blood vessels, meaning that individuals with severe symptoms, up to and including shock, are not typically seen.

Causes

Chikungunya virus, an RNA virus belonging to the genus alphavirus and family Togaviridae, is the cause of illness and is spread by Aedes aegypti and Ae. albopictus mosquitoes.

Transmission

Aedes aegypti mosquitoes are the primary transmitters of chikungunya virus. When they bite a person in the high fever stage, when the virus is in the bloodstream, it enters the mosquito's stomach and multiplies. The virus then travels to the mosquito's salivary glands, and when the mosquito bites another person, it transmits the infection, causing them to develop symptoms of the disease.

Incubation Period

Generally, about 1–12 days but commonly 2–3 days

Infective Stage

During the second to fourth day of the high fever phase, there is a large amount of virus present in the bloodstream.

Signs and Symptoms

The patient may experience a sudden high fever and a red rash on the body that may be accompanied by itching. Additionally, red eyes (conjunctival injection) may be observed, though bleeding in the whites of the eyes is rare. In children, the symptoms tend to be less severe than in adults, where the most prominent symptom is joint pain, which can occur in different places and may be accompanied by inflammation. In some cases, the joint pain is so severe that the joints cannot move. Generally, the symptoms resolve within 1-12 weeks, though in some cases the joint pain can recur 2-3 weeks later or last for months or even years. No patients with severe to shock symptoms were found, and unlike dengue hemorrhagic fever, a positive tourniquet test and petechiae may be seen on the skin.

Difference between DF/DHF and Chikungunya Infection

1.             High fever is more acute in Chikungunya than in DF/DHF and therefore the patient comes to the hospital sooner.

2.             Fever duration in chikungunya is usually shorter than in dengue and DF/DHF, with patients having fever durations as short as 2 days. In comparison, fever in DF/DHF typically subsides in 4 days.

3.             Although blood spots and a positive Tunigue test can be found on the skin in cases of DF/DHF, both spontaneous and test-induced numbers are usually less common.

4.             A convalescent petechial rash with whitish rings is not a symptom of Chikungunya.

5.             Chikungunya is associated with a higher incidence of maculopapular rash and conjunctival infections than is seen with dengue.

6.             Myalgia / arthralgia are more common in Chikungunya than in dengue.

7.             Up to 15% of those infected with Chikungunya experienced convulsions due to sudden high fever, which was three times higher than the rate of convulsions associated with high fever in dengue cases.

The Chikungunya virus infection, which originated in Africa, was first detected in Asia in 1958 by Prof. W McD Hamnon in Thailand at the same time as a dengue fever epidemic. Chikungunya isolates were also obtained from pediatric hospital patients in Bangkok. Children’s hospital patients in Bangkok.

In Africa, Chikungunya is found in many countries and is transmitted in two ways. The first, known as the primate cycle (rural type), involves humans, mosquitoes, and monkeys such as Cercopithicus or Barboon, which act as amplifying hosts. This can cause sporadic cases and small outbreaks (miniepidemics). The second way is the urban cycle (human-mosquito), which occurs when a non-immune person enters an area where the virus is present and then transmits it to the urban population through mosquitoes such as Aedes aegypti and Mansonia aficanus. This is particularly likely in areas where Aedes aegypti is very prevalent.

In Asia, the transmission of the disease is distinct from that in Africa. The primary route of transmission is urban, with Ae. aegypti being the primary vector. After the first report of the disease in Thailand, it has been reported in a number of other countries in Asia, including Cambodia, Vietnam, Myanmar, Sri Lanka, India, Indonesia and the Philippines, with the epidemiology following a similar pattern to other diseases caused by Ae. aegypti.

Rainy season is a time when the prevalence of this disease is high due to an increase in the mosquito population and the resulting infections in Aedes mosquitoes. This particular disease is not age-specific and can affect people of all ages, unlike dengue fever and rubella, which usually occur in individuals under the age of 15. In 1993, there were three outbreaks of this disease in Loei Province, Prachin Buri and Nakhon Si Thammarat as well as Nong Khai.

Treatment

There is no specific cure for the condition. The primary focus of treatment is palliative care, which includes medications to reduce fever, joint pain, and rest to help manage the symptoms.