Why did Exponential Growth Stop in India? We examine the evidence. The answer to this question has broader implications as Arcturus spreads, leading to hospitalizations, deaths and more Long COVID.

New Study: Children can significantly contribute to onward transmission, acting as the potential source of spread in the community.

The very contagious and immune evasive Arcturus (XBB.1.16) variant has been ripping across India from late January through till now. The new deaths continue to climb.

Thankfully, the deaths may slow down because the exponential growth we were seeing stalled out around April 21 2023 and started declining April 24th.

Why did the exponential growth stop?

This is an important question to answer as the Arcturus (XBB.1.16) variant is spreading in countries around the world. In the U.S., XBB.1.16 is gaining in prevalence, reaching between 10% and 25% as of April 29th CDC data. This will likely jump to between 20% and nearly 35% by May 5th and may be over 60% in many areas by May 12th. In Australia, hospitalizations continue to climb.

Below, India’s exponential growth has stalled and cases are declining in many areas.

While cases and hospitalizations didn't reach the same record-breaking levels as in 2021, they did rise to the highest levels seen in the prior seven months. One factor contributing to lower number of cases and hospitalizations is the significant decrease in testing compared to the first two years. Despite a population of over 1.4 billion people, the number of daily tests maxed out at just over 200,000 in the past week, and many hospitals were only testing the more severe cases. In fact, many states have been reporting zero cases and deaths, not because COVID-19 is absent, but because they aren't testing enough. Consequently, it's likely that millions of infections and an unknown number of deaths have gone unreported. However, the critical question is why cases are declining in the areas where testing is still taking place, primarily within a few cities and the surrounding areas of fewer than a dozen states.

What could cause the exponential growth of COVID-19 to stop? The options are limited: either everyone was infected with the variant, and a population-level of immunity was built without a significant increase in hospitalizations - which is plausible given its high transmissibility and the holiday’s - or a change in behavior decreased the available paths of transmission in mid-April, affecting the number of people becoming symptomatic and seeking testing, resulting in a decline in cases.

As it turns out, record heat swept across the country in mid-April, prompting the closure of schools in entire states, and in other states, morning classes were dismissed before 11 am. School closures do significantly reduce the available paths of transmission. While ending classes before lunch would have a lesser impact, it would still significantly reduce transmission. Most schools in India close for summer break in late April or in the beginning of May, which extends until sometime in June, depending on the school. If school closures caused cases to decline now, then it's plausible that it happened before. Let’s take a look at May 2021.

We can see that in 2021, cases increased until the beginning of May, then exponential growth stopped. This is solid supporting evidence that closing schools stopped the exponential growth but seeing it happen again in 2022 would provide more assurance we are on the right track.

Once again in 2022, cases were growing exponentially until the beginning of May. Could it be another coincidence? In 2022, new cases started increasing again at the beginning of June. Let’s look to see if schools reopened in early June. “The summer holidays in 2022 for Maharashtra schools are scheduled from May 2 to June 12 for Classes 1-9 and 11””Summer vacations in Odisha were cut short by 35 days this year (2022) and have been announced (to return) for June 6 to June 16” It appears that schools did return in early June 2022 and just might be why cases started increasing again.

As we can see on the graph below, exponential growth continued until July 22, 2022. That isn’t normally a time of year schools close but maybe they did. On July 13, 2022, an article said that Manipur schools would be closed until July 24th amid a COVID surge. That would provide enough time for children to clear the virus, resetting the exponential curve back to or below the community rate or base rate. This allows cases in households without children to decline. When children return to school, the exponential growth begins again but can take 2 months until the cases become visible through testing of symptomatic cases, who tend to be the older adults.

An article from June 30, 2022 tells us that the schools, and other educational institutions, cinema halls, and gyms throughout the country will remain closed until July 31, 2022. This was issued by the ministry of home affairs (MHA). Together, this explains why cases started declining again by July 22, 2022.

Meanwhile in 2023, the middle of April saw a heat wave that sent temperatures higher than 104 degrees (40C), prompting government leaders to close schools early for the summer break.

Reuters reported on April 18th 2023, that at least two states, Tripura in the northeast and West Bengal in the east, ordered schools to shut this week, as temperatures rose more than 5 Celsius above normal. It is reported that “the Delhi government has already advanced summer vacation in all schools of the national capital. The vacation, which was to start from May 11, began on April 20th.”

“The Arunachal Pradesh government has decided to close all the schools, including hostels, from April 26. The internal examinations conducted so far in the govt schools would be counted for assessment of students, and the tests scheduled on or after April 26 have been cancelled. The summer vacation in all state-run schools will end on May 31.”

“Maharashtra Government has announced School Holidays for all state board schools in the state. The schools would be closed from tomorrow - April 21, 2023 till June 15.”

“Coincidentally”, the exponential growth started to stall on April 21st and began declining by April 24th.

The extreme heat wave closed schools completely or shortened days on a massive scale across the country, and considering that cases declined as schools closed for summer break the prior two years, it is highly likely that exponential growth stopped due to the school closures. What do you think caused the exponential growth to stop? Vote Below.

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The new study below adds more fuel to the idea that transmission between classrooms and homes, students to siblings, to new classrooms, to new homes, and so on, could be significant enough to stop exponential growth when schools close.

Widespread household transmission of Omicron from Children

This study, published April 20, 2023, goes over contact tracing data that started with a 10 year old. This child goes to school and then to Taekwondo while pre-symptomatic. They found that within 3 weeks, 75 households became infected, resulting in 88 infections. The secondary attack rate was ~40%, asymptomatic or symptomatic.

"The study demonstrated that children can significantly contribute to onward transmission to their households, acting as the potential source of spread in the community."

The study went on to say, "In summary, the magnitude of the outbreak illustrates how younger children infected from diverse pediatric facilities can be a major source of widespread household transmission with the potential to facilitate community transmission in the era of omicron variant. As the virus evolves towards higher transmissibility, public health and social measures targeted at children should be adjusted to mitigate the impact of transmission in households and communities."

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Please let us know what you are seeing or if you have any other insights or questions.