Epidemiology of Chikungunya in Indonesia

*Tri Baskoro Tunggul Satoto and Nur Alvira Pascawati*

### **Abstract**

Chikungunya is a zoonotic disease which is caused by the Chikungunya virus (CHIKV) and transmitted by infected *Aedes spp* mosquito. In Indonesia, CHIKV is a re-emerging disease, which means that it is a disease that has gone for a long time, but then it spreads again and causes outbreaks frequently. CHIKV presence in Indonesia was first reported in 1979 in Bengkulu City causing substantial acute and chronic morbidity. After disappearing for 16 years, the CHIKV outbreak spreaded again in 24 regions throughout Indonesia from 2001 to 2003. In 2009 and 2010, CHIKV outbreaks hit western and central regions of Indonesia and increased from 3,000 cases per year to 83,000 and 52,000 cases per year. The burden of this disease is unclear due to insufficient monitoring and diagnosis. The spread and transmission of CHIKV in Indonesia is very high, due to travel, competent vectors, and the vulnerability of the population. In addition, the evolution of viruses, globalization and climate change has accelerated the spread of this virus. Effective antiviral treatment and vaccines do not yet exist, so early detection and appropriate management can help reducing the burden of this disease. Monitoring and risk assessment to reduce human-vector contact are also needed to reduce the impact of chikungunya.

**Keywords:** Indonesia, CHIKV, re-emerging disease, epidemiology

#### **1. Introduction**

Chikungunya is a zoonotic disease caused by the Chikungunya virus (CHIKV), and transmitted by infected *Aedes spp* mosquito. CHIKV is an important but often overlooked cause of fever in the tropics and subtropics [1, 2]. The disease is of little interest in the medical community and causes less fear when compared to other arboviruses such as DENV. The reappearance of CHIKV after a long absence has only recently attracted global attention because of its explosive attack, rapid spread, high morbidity, and various clinical manifestations [3–6]. However, the diagnosis of CHIKV is still very low due to overlapping clinical presentation with DENV and other endemic infections [7] as well as the lack of capacity for CHIKV testing [8]. Viral evolution, globalization, and climate change can further accelerate the spread of CHIKV, whereas specific antiviral treatments and effective vaccines do not yet exist [9].

In Indonesia, CHIKV is a re-emerging disease, which means that it is a disease that has gone for a long time, but it then spreads again [10]. Evidence from historical reports indicates that the first spread of CHIKV occurred in 1779 in Jakarta, but at that time the disease was referred to as kidinga pepo [11, 12]. This is widely recognized by arbovirus experts as the first report on chikungunya in Indonesia,

although it cannot be proven by molecular analysis [13]. Virologically confirmed chikungunya outbreaks were first reported in June 1982 in Jambi province on the island of Sumatra, followed by outbreaks between 1983 and 1984 [14]. CHIKV was no longer recorded in Indonesia for about 20 years, before the infection reemerged and caused several outbreaks in South Sumatra, Aceh and West Java in early 2001 [15]. In 2009 and 2010, CHIKV outbreaks hit western and central region of Indonesia started from approximately 3,000 cases per year increased to 83,000 and 52,000 cases per year [15–26]. After 2010, detected cases fell to 3,000 per year. Except during outbreaks, the number of cases are likely to be underestimated because diagnosis is often based solely on clinical presentation [27, 28].

#### **2. Epidemiology**

Arboviruses are viruses that undergo a cycle of transmission between a bloodeating arthropod vector and reinforcing vertebrate host. Mosquitoes are the main vector of arbovirus transmission and human involvement in the transmission cycle is incidental [29]. It is estimated that 3.9 billion people in 120 countries are at risk of being infected with one of the three main arboviruses, namely: namely CHIKV, Dengue virus (DENV) and Zika virus (ZIKV) [30]. An outbreak of chikungunya with specific features was first reported in the Southern province of Tanzania's Tanganyika region in 1952 [31, 32]. Later sporadic outbreaks of chikungunya were identified in parts of Africa and Asia during the 1950s and 1960s, followed by a clear comeback in the 2000s [33]. Since 2005, large-scale outbreaks of chikungunya have hit the southwest Indian Ocean and Southeast Asia [34–43]. In La Réunion, the outbreak affected about a third of the population [35, 44], and in India the virus infected more than 1.3 million people during 2005–2006 [45] and CHIKV then spread to Southeast Asia including Indonesia.

#### **3. Definition**

The diseases caused by CHIKV are clinically difficult to distinguish and accurately diagnose from diseases caused by DENV solely on clinical symptomps [46, 47]. Although previous literature has shown that, the proportion of symptoms in people infected with CHIKV is higher than DENV [48], however a systematic review shows that asymptomatic chikungunya has very wide variability with a percentage of around 3,2% during 2005–2006 in La Réunion to 82,1% during 2012–2013 in Philippines [49]. The definition includes four categories of cases: (1). Clinical case of acute, characterized with fever (temperature above 38.5° C/101.3° F]) and arthritis or joint pain (sometimes disabling) with epidemiological criteria and/or acute onset and laboratory criteria; (2). Atypical case, characterized with laboratory confirmed clinical cases accompanied with other manifestations (ie, cardiovascula, neurological, ophthalmological, dermatological, hepatic, renal, respiratory, or conditions of hematological); (3). Cases of severe acute, characterized with laboratory-confirmed clinical cases of CHIKV with life-threatening abnormal function of minimal 1 organ or system and requiring inpatient; (4). Chronic cases of suspected/confirmed, characterized with a previous clinical diagnosis of chikungunya 12 weeks after onset of symptoms and indicating at least 1 rheumatological manifestation (ie, edema, stiffness, or pain) that was persistent or recurring [50].

The highest CHIKV genotype in Asia has been noted to be asymptomatic found in Philippines with a percentage of 82.1% [51]. Common symptoms of chikungunya include high fever, severe joint and muscle pain, rash, photophobia and

*Epidemiology of Chikungunya in Indonesia DOI: http://dx.doi.org/10.5772/intechopen.98330*

headache [52, 53]. Severe symptoms implicated vital organs may develop during infection, like encephalitis [54, 55], myelopathy, myelitis [55], encephalopathy [55–57], neuroretinitis [58], optic neuropathy and Guillain's Syndrome [55, 58]. Barré [55, 58], myocarditis [57], hepatitis [59], acute interstitial nephritis [60], severe sepsis, septic shock [61] and multi-organ failure [57–59, 62, 63]. In rare cases, infection can be fatal [44, 59–61, 63]. Perinatal CHIKV infection can cause symptoms such as microcephaly and cerebral palsy [64]. In adults with persistent arthralgia/arthritis, alopecia and depression are the other symptoms most frequently noted [65–67]. A meta-analysis found that about 25% of chikungunya cases caused chronic inflammatory rheumatism and 14% had chronic arthritis [68].

#### **4. Incidence and mortality**

Eleven annual reports from the Indonesian Ministry of Health (MoH) were identified between 2004 and 2019 [15, 17–26]. These data show that the lowest incidence rate of CHIKV occurred in 2005 with 0.16/100,000 person-years [15] while the highest incidence rate was recorded in 2009 to 36.2 cases per 100,000 person-years [23]. In 2009, more than 83 thousand cases CHIKV in Indonesia was reported circulating in 17 of 34 provinces (50%) [23]. Cases began to decline in 2010 with 52,703 cases and continued to decline significantly until 2018, but again increased in 2019 with an incidence of 5,042 cases (**Figure 1**), but some districts did not report cases of chikungunya [69]. Based on a report from the MoH, this increase was due to relatively humid weather conditions with high rainfall, long periods of rain and immunity in areas that had been affected [69].

The case map by province showed that the CHIKV was not evenly distributed across Indonesia. The highest incidence of chikungunya occurred in Sumatra, Kalimantan and Java. However, Papua and West Papua provinces of Indonesia did not report chikungunya in 2008 and 2016. The shift in cases in several Indonesian provinces in 2019 has changed with the highest cases in West Java, Lampung and Gorontalo.

CHIKV cases that occurred in Indonesia during the 26 years period (1989–2014) actually originated from several countries. During that period there were 195 cases of chikungunya reported from travelers returning from Australia (128 cases) [70–77] Taiwan (47 cases) [47, 78–79], Japan (4 cases) [80–81] and other countries.

#### **Figure 1.**

*Trend and number of chikungunya cases based on the Ministry of Health report of the Republic of Indonesia from 2010 to 2019.*

in Asia, Europe and the Pacific (16 cases) [82–88]. Based on the results of investigations on five outbreaks that occurred, there were no reports of deaths due to chikungunya [40, 45, 64, 89, 90]. In addition, in eleven annual reports from the Indonesian MoH, for 44 years (1973 to 2016) there were also no deaths related to CHIKV infection [39, 41, 42, 44, 46–49, 51].

#### **5. CHIKV genotype circulating in Indonesia**

Sixteen studies that reported on the CHIKV genotype identified circulating in Indonesia were 130 viral sequences [27, 38, 47, 78, 79, 82, 87, 88, 91–98]. There were seven studies conducted on local populations [27, 28, 38, 91, 93, 96, 98] and eight studies with viruses isolated from travelers returning from Indonesia [47, 78, 79, 83, 87, 88, 92, 97]. One study did not specify whether the virus was isolated in local residents or in travelers [82]. Of the seven studies, four were conducted in non-outbreak conditions [27, 28, 93, 96], two investigations were carried out during an outbreak of chikungunya [38, 91] and one study did not specify the condition [99]. Most of the viruses isolated from travelers originated in Taiwan [47, 78, 79]. Another virus was collected from travelers returning from Singapore [92], France [97], the Netherlands [82], Russia [83], and Germany [88]. Most of the CHIKV isolated from Indonesia belonged to the Asian genotype and partially from the ECSA genotype. Of these ECSA viruses, two were isolated from local residents in 2011 [38] and eight others were isolated from travelers returning from Indonesia between 2008 and 2010 [47, 87, 92]. The ESCA virus sample during the 2008–2011 period in Indonesia was included in the Indian Ocean Lineage (IOL) because in the same period it was also circulating in Southeast Asian countries such as China, South Korea, Malaysia, Sri Lanka, Thailand, Singapore, and Myanmar [93].

#### **6. Vectors of CHIKV**

The vector that plays a role in CHIKV and DENV is the *Aedes aegypti* mosquito and the potential vector is the *Aedes albopictus* mosquito (The Asian Tiger Mosquito) [25]. The *Aedes* mosquito is a mosquito that belongs to the Diptera order and has more than 950 species [100]. Transmission of the disease caused by the *Aedes* mosquito can manifest itself in humans and animals. The *Aedes* mosquito usually lives in temperate and tropical climates. However, due to the current uncertain climate change, this mosquito is able to expand its habitat [100]. The following is an explanation of the mosquito that transmits CHIKV:

#### **6.1 Taxonomy**

*Kingdom: Animalia. Phylum: Arthropoda. Class: Insecta. Order: Diptera. Family: Culicidae. Subfamily: Culicinae. Tribes: Aedini. Genus: Aedes. Species: Aedes aegypti and Aedes albopictus.*
