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Opinion

Covid-19: what you need to know today

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The fact that a handful of people who flew to various parts of India from the UK have tested positive for the coronavirus is cause for alarm simply because these infections were discovered at the time India adjusted its inbound traveler screening process. . It is very likely that during the last seven months, since India restarted flights to and from other countries through so-called travel bubbles, there has been a steady trickle of infected people within (and also outside) the country. The selection process was toughened after panic over the new Sars-CoV-2 virus strain identified in the UK (as early as September, although only in recent weeks has it made headlines after becoming the dominant strain in the UK United). country, and causing an increase in infections). UK officials have said the new strain is 70% more contagious (or infectious) than the old one. They also say that in many parts of the country, it has become the dominant strain. That would mean that at least some of the people identified as Covid-positive in Monday’s test at airports could potentially be carrying the new strain.

Indian health officials insisted in a briefing on Tuesday that the new strain has not been detected in India, but this is one of those statements that is economical with the truth. The reality is that India doesn’t sequence enough viral genomes for this to be said with any certainty, but in all the briefings (and it’s usually the same people who are in charge of India’s Covid response) that I’ve heard on I have never heard the terms “we don’t know” or “we can’t say for sure”. In fact, what they lack in knowledge, these people often make up for with certainty. The correct answer, for example, to a question about whether the new strain is in India would be: it has not been identified in our tests, but we did not sequence enough viral genomes to say so for sure; now we are increasing the volume of genomes we sequence. That wasn’t that difficult, was it? As I wrote in Tuesday’s column (Dispatch 230), given that the new strain has been around since September and flights have been operating between various airports in the two countries, it is very likely that the strain is already in India, but we don’t know. Safely.

In Tuesday’s column, I wrote about how the UK had a fluke: one of the commonly used RT-PCR tests showed only fragments of two genes in the result, compared to the three it usually does. One of the 17 known mutations of the new strain was responsible for this. The reverse transcription polymerase chain reaction or RT-PCR test is considered the gold standard when it comes to diagnostic testing for Covid. It identifies viral RNA (ribonucleic acid, the genetic material) by converting it into complementary DNA, which it does using an enzyme called reverse transcriptase. Then a series of chemical reactions are used to amplify the complementary DNA sections. The amount of viral DNA is then measured using fluorescent markers. The test in question in the UK was calibrated to check for three different RNA targets and, due to the mutation, only found two. Ergo, the country didn’t really have to keep sequencing viral genomes to find out if the infection was caused by the new strain; If a test showed only fragments of two genes in the result, it indicated that the virus was the new strain.

In addition to vigorously sequencing more viral genomes, India would do well to collect more information (for example, each RT-PCR test also measures viral loads) from the molecular tests it performs (rapid antigen tests, apart from being unreliable, they are not). very useful in this context) rather than just treating the output as a binary yes / no. In fact, if there had been a system to do this, health officials here might have been in a better position to answer the original question: is the new strain in India?

Hindustan Times

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