On Sunday, doctors treating COVID-19 cases in Indore claimed that a more virulent strain may be wreaking havoc in the city, which has emerged as the coronavirus hotspot in Madhya Pradesh. They said samples from Indore, where COVID-19 has killed 57 people, will be sent to the Pune-based National Institute of Virology (NIV) to confirm their apprehensions of the strain being deadlier than in other parts of the country. "We have a feeling the strain is definitely more virulent in Indore belt. We have discussed this with the NIV and will be sending samples for them to compare by extraction of virus genome," Dean of Government Mahatma Gandhi Memorial (MGM) Medical College Jyoti Bindal told PTI. "There are also other factors also for the high fatality rate, like patients turning up at the hospitals late," she said.
Jitendra Bhargava, director of the state government-run School of Excellence in Pulmonary Medicine, also shared Bindal's concern, saying the high mortality rate in Indore needs to be investigated through viral culture and RNA extraction.
Though there is no concrete scientific proof of a palpable divergence in mortality rates caused by different strains of the coronavirus (age, lifestyle, co-morbidities and severity of the symptoms at the time of hospitalisation all play a major role in determining the fatality rate), a study from China had found the presence of different strains of the virus which it named 'L' and 'S' strains.
What are the different strains of the virus?
According to a study, 'On the origin and continuing evolution of SARS-CoV-2', published in National Science Review, the more aggressive L type of coronavirus was found more in the early stages of Wuhan outbreak, but its frequency decreased due to human intervention. "Population genetic analyses of 103 SARS-CoV-2 genomes indicated that these viruses evolved into two major types (designated L and S), that are well defined by two different SNPs that show nearly complete linkage across the viral strains sequenced to date. Although the L type (~70%) is more prevalent than the S type (~30%), the S type was found to be the ancestral version."
"Whereas the L type was more prevalent in the early stages of the outbreak in Wuhan, the frequency of the L type decreased after early January 2020. Human intervention may have placed more severe selective pressure on the L type, which might be more aggressive and spread more quickly. On the other hand, the S type, which is evolutionarily older and less aggressive, might have increased in relative frequency due to relatively weaker selective pressure," according to the study.
'L-type strain' in Gujarat
The dominance of this more aggressive Wuhan L strain is what experts now hypothesise is causing the higher COVID-19 mortality rates in Gujarat, which has reported 133 deaths so far. However, no research has been conducted to confirm this, they said.
A scientist at the state-run Gujarat Biotechnology Research Centre (GBRC) said that the novel coronavirus used for genome sequencing recently conducted by it was found to contain the L-type strain. "Analysis done by scientists abroad has shown that the L-type strain has been dominant where more mortality is reported among coronavirus patients. This strain was found to be more prevalent in Wuhan," director of GBRC, C.G. Joshi, said.
"The coronavirus sample we collected from a patient for genome sequence contained the L-type strain. This strain has a much higher virulence as compared to the S-strain," he said. "Variation in coronavirus is in terms of number and percentage of mutations. As per the analysis, the L-type strain is dominant where more mortality is reported. Scientists have earlier found that this strain has caused more deaths," he said.
The GBRC recently succeeded in decoding the entire genome sequence of the novel coronavirus, and identified its three new mutations.
The Indian Express had reported Atul Patel, an infectious disease specialist at the Sterling hospital, as saying that the mortality rate was low in Kerala because most of the patients came from Dubai which has the milder S strain. He said, according to publication, that Kerala has more cases of the S strain, while the L strain was more common in Italy and France, causing rapid death. “In the US, the New York data is entirely different from the rest of its states. Patients from New York were all travellers from Europe."
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So far, no study has been conducted in India to establish which strain of coronavirus is predominant in patients here.
Again, to emphasise, no study has been conducted to back up the hypothesis of a marked increase in death rates caused by difference in strains of the coronavirus. The Gujarat state government has also attributed the high mortality among coronavirus patients in the state to co-morbidities and high risk factors. Heart and lung diseases, diabetes, and hypertension, are among common diseases that have been found among COVID-19 patients who passed away in Gujarat. The risk factors includes patients in the age group of above over 60 years and under five years of age, and pregnant women, and they account for 90 per cent of patients who passed away, Principal Secretary (Health), Jayanti Ravi had recently said.