Chikungunya- An Update
Correspondence Address :
Dr. Sujata M Byahatti
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Chikungunya is an arboviral disease which is transmitted by the bite of the Aedes mosquito, which recently reemerged as a massive epidemic in the Indian Ocean islands and India. Chikungunya is generally considered as a self-limiting disease and has been reported to be non-fatal. The Chikungunya virus (CHIKV) was isolated in Tanganyika (now Tanzania) in 1953. Chikungunya outbreaks were reported in India in 2005, and 1.4 million Chikungunya cases were reported from different states. This disease has reemerged in India after 32 years. It should be pronounced as CHICK_EN_GUN_YAH not as CHICKENGUINEA. There are many cases which have been noted, but very few deaths have been reported. The lack of any official reports of the deaths could remain as a poor recording of the âCauses of Deathâ in India. Correct reporting, recording and monitoring are essential for the screening of this disease for the purpose of the proper management and the prevention of the spread of this disease.
Chikungunya fever, epidemic, polyarthritis.
Chikungunya virus (CHIKV) was isolated in Tanganyika (now Tanzania) in 1953(1). The name is derived from the word âMakondeâ, meaning 'that which bends up', with reference to the stooped posture which develops as a result of the arthritic symptoms of the disease (2), (3). In Asia, this virus is transmitted almost exclusively by Aedes aegypti mosquitoes. India had its first CHIKV outbreak in 1963, which was followed by epidemics in other parts of the country (4). Recently, massive outbreaks of CHIKV have been reported from many islands in the Indian Ocean (5). Like CHIKV, the dengue virus (DENV) is also transmitted by Ae. Aegypti and is endemic to the urban and semiurban areas of India (6). In Asia, the CHIKV-affected areas overlap with the DENV-endemic areas (7), (8) and provide opportunities for mosquitoes to become infected with both the
viruses. The co infection of CHIV with (4) dengue viruses (DENV-1 and DENV-4) was reported in Puerto Rico in 1982 (9). Since then, many cases of concurrent infections with multiple DENV serotypes have been reported in many countries.
The aim of the present article is to enlighten the health professionals in detail regarding the epidemiology, clinical features with the mode of spread, complications, different treatment modalities and precautions which need to be taken to prevent the spread of the disease.
This disease was first described by Marion Robinson and W.H.R.Lumbsden in 1955, following its outbreak on the Makonde Plateau, in 1952 (10).
Recent search by the Pasteur institute in Paris claims that the virus has suffered a mutation that enables it to be transmitted by Aedes Albopictus (Tiger Mosquito). Chikungunya is closely related to the Oânyongânyong virus (10). Chikungunya is a dengue-like disease which is transmitted by the Aedes, Culex and the Mansonia Mosquitoes (11). âChikungunyaâ is a local word, meaning âDoubling Upâ, owning to the excruciating joint pains (12).
Clinically (10) the patients develop fever which can reach 39 degree Celsius. The fever lasts for 2 days and comes down. Petechial or maculopapular rashes are noted, involving the limbs and trunk, and arthralgia or arthritis affecting multiple joints are observed, which can later be debilitating. However, joint pain, intense headache, insomnia and an extreme degree of prostration lasts for about 5-7 days; other manifestations include nasal blotchy erythema, lymhoedema over the acral area, nasal blotchy erythematic, multiple echymotic spots, vesiculobullous lesions, sublingual hemorrhage, photourticaria and acral urticaria. Orally, lichenoid eruptions, apthous ulcers and freckled pigmentation over the facial area are noted in some cases (10).
Chikungunya virus is an important human pathogen, a member of the Alphavirus genus in the family of Togaviridae, which causes a syndrome which is characterized by fever, chills, headache and severe joint pain, with or without swelling (usually the smaller joints). Chikungunya fever outbreaks had affected many countries since January 2005. The outbreak which occurred in 2006, appeared to be the most severe and one of the biggest outbreaks which was caused by the chikungunya virus (CHIKV) in India, affecting over 13 lakh people (13), (14). This disease was first described in 1955, following an outbreak on the Makonde Plateau, along the border of Tanganyika and Mozambique (15). The Chikungunya virus is no stranger to the Indian subcontinent. Since its first isolation in Kolkata (16), (17) in 1963, there have been reports of its incidence from different parts of India viz. Vellore (18), Chennai (19), Nagpur (20), Barsi and Solapur District (21). Since the last outbreak of chikungunya fever, there had been hardly any active or passive surveillance which was carried out in our country, which suggested the disappearance of the virus from the subcontinent. However, large scale outbreaks of fever which have been caused by this virus in several States of India, including Andhra Pradesh and Maharashtra, have confirmed its re-emergence (22). Recently, massive outbreaks of CHIKV have been reported from many islands in the Indian Ocean (15). Since 2005, co-infections with DENV serotypes have been reported in Delhi, India (23). Co-infections with DENV and CHIKV were reported in Calcutta, India, in 1967 (24). Subsequent serological investigations in southern India indicated that the 2 viruses can coexist in the same host (25). For many years, it appeared that CHIKV had disappeared from India, but late in 2005, the virus reemerged on Reunion Island and in India (22). Confirmed cases of CHIKV infection have been reported from Delhi, Haryana, Uttar Pradesh, and Rajasthan provinces in northern India, although these states did not have large-scale epidemics (26). DENV infections are endemic to northern India; in recent years, increasing trends of the co circulation of multiple DENV serotypes in Delhi, suggest that DENVs are becoming hyper endemic to this region (23). During 2006, DENV and CHIKV were detected in Delhi (26). Because the clinical features of DENV and CHIKV are similar, CHIKV infections may go undiagnosed in the DENV-endemic areas. In India, the Ae aegypti mosquitoes are the primary vectors for DENV and CHIKV, and opportunities for co-infections in humans are increased by the feeding behaviour of the mosquito (27), the low socioeconomic conditions, and the high population density.
Various complex diseases (28) are generally influenced by more than one gene or an environmental factor, and as a consequence, do not exhibit a simple mode of inheritance. In community, although only a small percentage of exposed individuals will develop the disease. Some individuals often show variation in the susceptibility/resistance to certain diseases. Therefore, host susceptibility, genetic factors and, possibly, environmental factors may be important for the development of these diseases. A study (29) noted that Rh positive blood group individuals are more susceptible than others. Among them, the blood group O +ve individuals are more susceptible to chikungunya than those with other blood groups. No blood group with Rh negative was found to be affected with chikungunya; it indicates that people with the Rh -ve group have more resistance to chikungunya. Chikungunya disease is an acute arboviral illness which is characterized by a sudden onset of fever, skin rashes and incapacitating arthralgia (30).
A suspected case (31) is confirmed by either the isolation of Chikungunya virus, or a detection of the antichik IgM in serum with a two fold rise in its titres, or by the detection of the CHIK nucleic acids in the serum by RT-PCR.
Human epithelial (32) and endothelial cells, primary fibroblasts and monocyte-derived macrophages are susceptible to infection with these viruses. Lymphoid and monocytoid cells, primary lymphocytes and monocytes and monocyte-derived dendritic cells are not susceptible to infection. Viral entry occurs through pH-dependent endocytosis. The infection is cytopathic and is associated with the induction of apoptosis in the infected cell. The infection is highly sensitive to the antiviral activity of type I and II interferonâs.
Spread of Disease
Chikungunya re-emerged in India in December 2005 after a gap of 32 years. The official figures from the Government of India indicate 1.39 million suspected Chikungunya cases from 152 districts across 10 states in India (33), (34). This epidemic disease has spread rapidly and has affected many communities with an attack rate of 40-60% (35). The most likely explanation of this rapid spread of the virus could be the lack of herd immunity in the population, unplanned development, poor public health systems- specifically the vector control systems and perhaps, a mutation in the virus. Recently, the first reported Chikungunya deaths on the RĂ©union Island took the French authorities and the world by surprise, as Chikungunya was previously considered to be non-fatal. French scientists reported a mortality rate of about 1 per 1000 cases on this island (36). The strains of the virus in this Indian Ocean Islandâs outbreak and in the Indian subcontinent were found to be of the same strain as that of the African sub-type. (37) Surprisingly, the Government of India has not reported any deaths in spite of 1.39 million officially reported cases.
The key (38) reasons for not finding any Chikungunya deaths could be due to:
1. Poor reporting of death, and the causes of death.
2. Lack of availability of blood testing facilities for the virus (with only two government institutes in the whole county). Only 13000 samples have been sent for testing out of 1.3 million suspected cases. Many hospital authorities are afraid to stamp a death case as Chikungunya without a positive blood test. Instead, such deaths are attributed to fever, viral fever, multi-organ failure or Cardio Respiratory Failure (CRF).
3. The clinical case definition of a Chikungunya death has not been developed or disseminated widely by any national/state health authority or any research institute.
4. No systematic efforts have been made to screen all the deaths during the epidemic to identify as to which of them were caused due to Chikungunya.
5. No system was developed to follow up the 1.3 million reported cases of Chikungunya to see if any of them had resulted in death.
The management of these patients is very essential, although diagnosis of these cases remains a difficult task, due to overlapping
features with that of other viral infections. The only symptomatic treatment in the form of analgesics (topical and systemic) provides a better result (10).
a. Vector control- The Aedes aegypti mosquito should be the main target of the control activities. It requires active community involvement to keep water storage containers free of mosquitoes and to eliminate other breeding places of the mosquitoes in and around houses and dwellings (41).
The organophosphorous insecticides abate are increasingly being used as laviceides. They can prevent breeding for up to 3 months when applied on sand granules, they do not harm man and they do not affect the taste of water. A new technique consisting of an aerosol spray of ultralow volume (ULV) quantities of malthion or sumithion (250 ml/hectare) has been found to be effective. These tiny droplets kill the mosquitoes in the air, as well as on water.
b. Vaccine: No vaccine has yet been developed, that has been considered as suitable for use (42), (43).
The controversy on Chikungunya deaths shows that India must take action urgently to improve the system of death registration and should also publish and make public mortality data on a weekly basis, with a proper cause- of- death analysis. This will be useful in predicting and understanding such epidemics better. This calls for a political and administrative commitment to strengthen the state, district and city/town offices of âregistrar of births and deathsâ and epidemiological units. It also calls for more training of doctors, nurses and medical record clerks to accurately report the causes of death. Strict monitoring and follow up of the reporting of the causes of death are needed. Non-reporting or misreporting has to be reprimanded to improve the situation. Hence, the Government of India, the WHO, the CDC, the Gates foundation and other global health leaders must invest in improving the death reporting and the epidemic analysis response mechanisms which are the basics of any public health system. If we do not improve the cause of death reporting, then in the future, more dangerous diseases like SARS and the Bird flu may spread wildly and kill many more people before these epidemics are even detected.
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