With daily Covid-19 cases doubling in Delhi over the past week, the national capital is now recording almost half of country’s fresh caseload. On Sunday, of the 2,541 cases in India, 1,083 were in Delhi.
Experts believe a combination of factors have led to the spike: the official relaxation in masks requirements, schools being reopened, more frequent social gatherings and highly transmissible sub-lineages of Omicron, among them.
Despite this, many do not believe this will result in a severe wave. Though the number of people infected with the virus in Delhi has doubled to 3,975 on Monday from 1,729 on April 18, the severity of infection that could lead to hospitalisation has been relatively low. On Monday, the number of those hospitalised had risen 30% to 107 from from 81 since April 18.
While it seems that a highly transmissible strain of the Omicron variant is circulating in the National Capital Region, it is difficult to predict whether the surge will continue to be intense, Dr Rajesh Pandey, a scientist at Council of Scientific and Industrial Research’s Institute of Genomics and Integrative Biology.
Experts say that the spread of the new sub-lineage could be limited because the last sero-survey in Delhi in November 2021 to ascertain the prevalence of the disease showed that 97% of the city’s population had antibodies against the coronavirus. Besides, India experienced an Omicron wave in January and February that gave a large section of the population additional immunity.
Low hospitalisation numbers
The present surge may have been encouraged by poor masking and increased crowding. “Malls, schools, theatres have reopened,” said Dr Amitabh Parthi, an internal medicine specialist in Fortis hospital in Gurgaon. “There are wedding functions happening. This makes transmission easier in dense pockets.”
Even people who have been administered booster shots are getting hospitalised, Parthi said. “This means the variant is able to bypass vaccine induced immunity,” he said.
Patients in the current surge are complaining of cough, cold, and fever and most are able to recuperate under home isolation. Those requiring hospitalisation are mostly aged over 70, with comorbidities like heart disease, diabetes, hypertension, and cancer, said Parthi.
Doctors said the current pool of Covid-19 patients is reporting new symptoms, most commonly diarrhoea, along with cough, cold and fever. Most are recovering within five days.
The need for and external oxygen support remains low.
On April 24, Delhi had 107 people hospitalised, of them five were on ventilators and 11 in intensive care units, up from one patient on ventilator and nine in ICU a week ago. While new cases have doubled over a week, hospitalisation number remain low.
Over 99% of Covid-19 beds in Delhi hospitals are vacant. Daily deaths hover between one or two, up from zero for several weeks. Parthi said the current variant seems milder than Omicron and indicates the severity of infection is slowly tapering out.
The present surge
On March 30, the virus’s reproduction value – or R value – crossed 1 in Delhi. The R value measures how many people on average are being infected by one Covid-positive person. An R value greater than 1 indicates a high transmission rate. In the week from April 5, the R value in Delhi touched 1.25 and was at 2.24 between April 11 to 21, highest for any city in India.
The daily caseload jumped from 137 on April 11 to 501 cases on April 18 and 1,083 cases by April 24. The city is conducting over 24,000 tests daily. The positivity rate – the percentage of all tests performed that are actually positive – touched 4.4% on April 24, up from 3% until a week ago.
Delhi is not the only city in the National Capital Region to record a high R value. Noida and Ghaziabad in Uttar Pradesh and Gurgaon in Harayana have noted a rise in cases. Harayana’s R value rose to 1.9 between April 9 to April 21, while it touched 2.05 in Uttar Pradesh between April 12 and April 21.
This sustained rise in the R value in Uttar Pradesh, Harayana and Delhi indicates a definite surge in the pandemic, said Sitabhra Sinha, professor at the Institute of Mathematical Sciences.
“In the last few days, the R value has crossed 1 in few other states. Maharashtra, Kerala, Tamil Nadu, and Karnataka show a rising trend but it is too early,” he said. “We need to wait and watch whether cases rise there and the trend continues.”
In Delhi, the rise in Covid-19 cases is suspected to be due to a strain that is a sub-lineage of Omicron. As the Omicron variant began spreading globally in November last year, it mutated into two sub-lineages: BA.1 and BA.2. According to the World Health Organisation, the BA.2 variant of Omicron remains a variant of concern. But while BA.2 has growth advantage over the first sub-lineage BA.1 and parent lineage Omicron, it is yet to be scientifically seen whether BA.2 is more severe than its predecessor.
In the US city of New York, further offshoots of BA.2 – BA.2.12 and BA.2.12.1 – account for 90% of cases currently. The BA.2.12.1 offshoot has also been found in Delhi. “Much is speculative but it seems this variant of Omicron lineage is present in higher proportion,” said Pandey, from Council of Scientific and Industrial Research’s Institute of Genomics and Integrative Biology.
The BA.2 has at least 29 mutations in the spike protein, higher than previous variants. One of those mutations, L452Q, is known to escape immune response and attach itself to host cells easily. Data from GSAID, a global database tracking mutations in coronavirus, suggests that BA.2.12.1 has been circulating in India for a few months already.
Sinha, from the Institute of Mathematical Sciences, said that the number of Covid-19 cases are rising more slowly now than the third wave in January and Febuiary fuelled by Omicron. While the R value had touched 4.82 in Delhi during the third wave, it has so far touched 2.24 in the current surge.
“Delhi was first to see a surge during the third wave,” said Sinha. “This time too it is the first to report a rise. The transmission is slower this time, which means it may last longer.” He added that the speed of transmission could be slowed if Indians start wearing masks again.
On April 18, the Uttar Pradesh government made masks mandatory in public places in Lucknow and six cities in the state that are part of the National Capital Region. On April 20, Delhi advised residents to mask in public places. Harayana, Punjab and Chandigarh have followed suit.
In Maharashtra, state health secretary Dr Pradeep Vyas said the government is yet to decide whether to make mask mandatory again. “Let us see how things unfold in next four-five days and then we will suggest to appropriate authorities,” Vyas told Scroll.in.
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