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Thursday, July 19, 2018

Why chikungunya slips under dengue radar

Chikungunya spreads round the year and is as prevalent as dengue, NIV finds after redefining symptoms

Written by Anuradha Mascarenhas | Pune | Updated: June 30, 2018 8:54:06 am
Why chikungunya slips under dengue radar Dengue and chikungunya are both mosquito-borne diseases and involve similar symptoms including high fever, headache, joint pain and rashes.

Chikungunya is as widely prevalent in India as dengue but tends to get overlooked or missed due to greater focus on dengue, a new study by the ICMR-National Institute of Viorology has found.

Cases of chikungunya were observed throughout the year while dengue spreads mainly during the monsoon, the study showed. Because of similar clinical symptoms, there is also greater difficulty in accurate diagnosis, Dr D T Mourya, director of NIV, main coordinator of the study said.

Dengue and chikungunya are both mosquito-borne diseases and involve similar symptoms including high fever, headache, joint pain and rashes. Dengue is much more dangerous. Last year, the National Vector Borne Disease Control Programme (NVBDCP) reported 1.9 lakh case of dengue cases and 67,700 of chikungunya. This year, 12,789 cases of chikungunya and 9,143 of dengue have been reported so far, but the latter count could jump in the ongoing monsoon.

NIV carried out a multi-site study as part of the Global Health Security Agenda, a partnership of over 50 countries. Data was collected between September 2016 and December 2017 from Sher-e-Kashmir Institute of Medical Sciences, Sawai Man Singh Medical College, King George’s Medical College, National Institute for Research in Tribal Health (Jabalpur) and Regional Medical Research Centres in Bhubaneshwar and Port Blair.

“Our study focused on generating more detailed information on the prevalence of dengue, chikungunya and cases of dual infections. The study also included detection of prevalence of Kyasanur Forest Disease (KFD) and Congo Crimean Hemorrhagic Fever (CCHF),” Pragya Yadav, principal investigator, told The Indian Express.
The researchers tested 6,479 patients with high fever. Of these, 1,068 tested positive only for dengue and 552 only for chikungunya. In 178 cases, patients tested positive for both diseases. “What we found surprising was that the prevalence of chikungunya was seen throughout the year, and in all seasons — pre-monsoon, monsoon and post-monsoon,” Yadav said.

For their study, the researchers also looked at a few additional symptoms that helped identify more positive cases for each disease. “Fever with vomiting or fever with breathlessness is not a typical symptom of dengue and chikungunya,” Yadav said. But including vomiting and other gastrointestinal symptoms increased detection.
For instance, using the NVBDCP case definition of dengue (fever with two or more symptoms like myalgia, arthralgia, headache and rash) the researchers could identify 706 cases of dengue. But inclusion of newer symptoms took the number of dengue positive cases for to 789. For chikungunya, the standard NVBDCP case definition led to detection in 516 cases, whereas using the modified case definition 644 patients could be detected.

“What is important is that the continuous presence of chikungunya and dengue positive cases suggest the presence of aedes vector of mosquito throughout the year in the community and not just during the monsoon season,” another researcher said.

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