[NEW DELHI] Mutations in chikungunya strains in India, and variations in genetic sequences of the virus, within and between Indian states, could offer vital clues on how the virus is constantly evolving and adapting to new mosquito vectors, researchers report.
The two mutant genes code for changes in two key proteins present in the envelope surrounding the virus. They were isolated from samples in Delhi that recorded its first major chikungunya disease outbreak from October to December in 2010
Chikungunya, currently endemic in south and central India, was first reported in the country in 1963. In 2005, the disease re-emerged in seven states, and in 2010, 3.7 million people were affected by the virus all over the country
But, the "number of cases has been grossly underreported due to mistaken diagnosis of dengue and non-reporting of suspected cases and related deaths," said a report in the Virology Journal on 25 May.
The report, by scientists from the Delhi-based International Centre for Genetic Engineering and Biotechnology (ICGEB), and Vardhman Mahavir Medical College and Safdarjung Hospital, was based on comparisons of genetic sequences of the virus isolated from patients in Delhi and eight other states.
Besides the two mutant genes, the researchers found considerable differences in sequences both within and between states, with maximum diversity in the western state of Maharashtra.
They also generated a 'molecular signature' – distinct sequences of 'nucleotides' or the chemical units that make up the genetic material and can help identify the strain
The researchers found that two Delhi mutants had a unique molecular signature that was different from those found earlier in the country, including strains emerging since 2005.
The emergence of a distinct molecular signature within the strains emphasises that "accumulation of mutations in the viral genome is leading to appearance of new subgroups and suggests a dynamic evolution of the virus," the report said.
Sujatha Sunil, principal investigator at the insect resistance group at ICGEB's plant biology division, said researchers have been trying to understand the considerable differences in symptoms shown by chikungunya patients across India.
Acute cases generally show low fever, severe joint pains and muscle pains, while chronic cases have arthritis for anywhere from 15 days to several years, she explained to SciDev.Net.
Some Indian patients have additionally been reporting complications such as stomach and intestinal problems and skin rashes, symptoms not reported previously anywhere, she said.
The new findings could help understand how the virus is evolving and adapting to new vectors. New mutations also appear to be masking previous chikungunya populations, and spreading much faster and more rapidly, she added.