Chikungunya Fever

Chikungunya in South-East Asia - Update

January 2008

In recent years, countries in the South-East Asia Region have been severely affected by the outbreaks of chikungunya (CHIK) fever. India was hit in 2006 after quiescence of 32 years. Indonesia, Maldives, and Sri Lanka have also been swept by this emerging infection. Various factors that have been incriminated to resurgence of chikungunya include mutation of the virus, absence of herd immunity, lack of efficient vector control activities, globalization and  emergence of Aedes albopictus, in addition to Aedes aegyptii as an efficient vector for chikungunya virus.

India

In 2006, more than 1.38 million cases of chikungunya were reported in India. During 2007, a total of 56365 suspected cases of CHIK have been reported from 14 states and Union Territories (UTs) in India. The state of Kerala alone accounts for 42.7% of the cases.

No death has been attributed to CHIK in India in 2007.

The National Vector Borne Diseases Control Programme undertakes surveillance of suspected CHIK cases through a network of 40 hospital-based sentinel surveillance centres supported by 13 apex laboratories. As per the national policy, 10% of the suspected cases should be confirmed for CHIK by appropriate laboratory tests. In 2007, 11.7% of the suspected cases were investigated and 21.4% of them were confirmed for CHIK cases. However, the proportion of reported suspected cases tested for CHIK and the proportion of confirmed cases varies in different states and UTs. The states of West Bengal and Gujarat have not reached the target of 10%, the proportion tested is high in states where there have been less number of cases such as Andhra Pradesh (39) and Goa (78). Among those tested, the proportion of confirmed cases varies in different states and is high in Tamil Nadu (76.9%) and Maharashtra (46.7%). 

In comparison to 2006, there has been overall decrease of 95.9% of reported suspected cases in India between 2006 and 2007. The drop has been consistent in most of the states in the range of 95-99%, but the percentage reduction in the cases is less in Delhi (19.3%), Kerala (66%), and Goa (72.8%).

The states of West Bengal and Lakshyadweep recorded higher number of cases in 2007 as compared to 2006.

The proportion of the suspected cases which were further investigated has increased from 1.1% to 11.7% between 2006 and 2007 and the proportion of confirmed cases has gone up from 12.5% to 21.4% during the same period.

Table 1: Number of reported suspected cases and confirmed cases of chikungunya in India- Year 2007

No cases were reported from Madhya Pradesh, Andaman & Nicobar  Islands and Pondicherry as compared to 2006 when 60,132, 1,549, and 542 cases were reported respectively from these three states/ UTs. Considering the epidemic nature of the diseases, it is possible that these figures represent the situation in the A&N Islands and Pondicherry, however it will need to be further investigated at least in Madhya Pradesh. It could be related to decreased reporting or inability of surveillance system to detect the cases.

Indonesia

In Indonesia, chikungunya occurred sporadically until 1985 after which there were no reports until a series of outbreaks between 2001 and 2007. Between January 2001 and April 2007, Indonesia reported 15 207 chikungunya cases from 7 provinces, with a peak in 2003. There have been over 1200 suspected cases of CHIK reported from 23 sub-districts in the year 2007. Most of the cases were reported from province of Jawa.

At the time of writing this paper, reports of an outbreak of suspected chikungunya in Indonesia (starting in December 2007) has been received, the details on the number of suspected cases is awaited.

Maldives

The  CHIK outbreak in Maldives started in December 2006 and lasted for three months. 10,831 (4.5% of the population) suspected cases of CHIK were reported in Maldives. The attack rate in Maldives ranged from 38-41%. Laboratory samples were taken from 67 patients, all of them were positive for CHIK; 21% of specimens were anti-CHIKV IgM positive and 96% were positive for CHIK virus in PCR testing. Suspected CHIK has been reported in Maldives in 2007 and in first four weeks of 2008 a total of 107 cases of suspected CHIK have been reported.

Chikungunya has established endemicity in several parts of South-East Asia Region. The socio-economic factors and public health inadequacies that facilitated the spread of this infection continue to exist. There is an urgent need to strengthen national surveillance and response capacity through multisectoral approach and active participation of the communities to prevent and contain this emerging infectious disease.