After the first Chikungunya fever outbreak in Bhutan on 30 July, a total of 215 samples were received by Public Health Laboratory (PHL) as of 31 August out of which 64 tested positive.
This is what the Public Health Laboratory (PHL)’s ‘Report on Chikungunya outbreak in Bhutan’ stated.
A total of 2515 fever cases were documented from four hospitals of Phuentsholing (62.5%), Samtse (23%), Sipsu (5%) and Gomtu (4.4%).
These hospitals which share borders with West Bengal saw an increase in fever from the 27th week which doubled in the 30th week. The Phuentsholing hospital records showed highest fever cases (70%) followed by Samtse.
From the 37 confirmed cases, clinical signs and symptoms shown by Chikungunya cases were fever (100%) followed by arthralgia (59%), headache (57%), generalized body ache (51%) nausea/vomiting (19%) and rash (8%).
The most common age group affected by Chikungunya fever was 15-44 years with 54.0% followed by 5-14 years.
The report states all first confirmed cases from four places (hospitals) can be assumed as an index however, those index cases could be confirmed as source to general population in four places.
“Both index case of Samtse and Gomtu had travel history to Birpara and Chamarchi, West Bengal but an index cases of Phuentsholing had no travel history to border town prior to onset of illness,” stated the report.
Chikungunya fever cases were initially seen in Birpara, West Bengal.
Later, the health team visited three nearby health centers in border towns (Newdoor hospital, Chanaburi and Chamarchi health Center) for verification and confirmation of the disease. It was later confirmed and notified to PHL and Ministry of Health (MoH) on 16 July.
Though the first three samples suspected for Chikungunya were sent by Samtse hospital (collected from a case by PHL on 12 July), but after further investigation the date of onset of illness was on 11 July and had a travel history via border towns of West Bengal en-route to Samtse from Thimphu on 9 July.
The report states the case was a resident of Samtse town and had to travel to Thimphu on 26 June for personal work. Based on information of the first case, it was concluded that transmission was imported because Chikungunya fever outbreak was confirmed by then in nearby towns (Birpara and Chamarchi).
It is said initially, CHIKV was said to be introduced in 2nd week but later investigations revealed that CHIKV must have probably been introduced earlier than anticipated because Phuentsholing hospital records have seen fever cases with severe joint pain, vomiting, and nausea from 1 July and similar cases were also seen in Samtse and Gomtu.
However the disease was officially reported on 30 July.
Case definition of Chikungunya fever outbreak
A person who visited Phuentsholing, Samtse, Gomtu and Sipsu hospitals was symptomatic of acute onset of high fever, temperature less than or equal to 38 degree Celsius, arthralgia/arthritis, polyarthralgia, nausea, vomiting, generalized body ache and macupapular rashes from 1 July to 18 August during the period of investigation.
Case definition was developed based on retrospective review of OPD fever cases from January to August and in-patient from May to August which included laboratory confirmed cases in four hospitals.
Chikungunya fever outbreak was said to be expected long time back in the country because both vectors (Aedes aegypti and albopictus) responsible for CHIKV transmission from human to human have been documented in the country since 2004 after an outbreak of dengue in Phuentsholing.
“From the experience of the current Chikungunya epidemic and influenza A/H1N1 pandemic in 2009, we realized that the country cannot be spared from epidemic and pandemic although it is remotely located and still isolated,” stated the report.
The public health surveillance is indispensible to monitor any unusual public health events and therefore needs to be strengthened together with the surveillance system including laboratory capacity to detect and confirm an etiology to response on time.