The exponential growth phase of the third wave is on in Odisha. A single positive is spreading the infection to nearly 6 others. The R-value and epidemic growth rate in the State are together hinting at an exponential rate of growth for the next fortnight.
The epidemic maths suggest the likely peaking of cases in Odisha in the first fortnight of February.
The daily growth rate of the country as of Jan 9, 2022, has started plateauing at 34.9 percent, which as per the report of Cambridge University, New Delhi-based Health System Transformation Portal and UK-based National Institute of Economic and Social Research, reflects the end of the super-exponential growth phase of the third wave.
The report observed, "Daily growth rates have peaked and are now clearly declining in Bihar, Chhattisgarh, Delhi, Jharkhand and West Bengal. In Jharkhand, the daily growth rate peaked at 57 percent on January 4, and has since declined to 23 percent. In Delhi, after peaking at 53 percent on January 5, the daily growth rate has declined to 36 percent."
And the report further added that based on the current trends, daily cases are likely to peak in the second half of January in Jharkhand and around January end in Delhi.
Odisha Peak Time - First Forecast
However, the scenario is not so optimistic in Odisha. The Cambridge University report has estimated the R-value for the State at an exponential 5.91 percent on Jan 9, 2022. And the filtered daily growth rate of the State has been estimated at a massive 44.4 percent.
Since the filtered growth rate of the State is on the rise ( from around 15 percent on Jan3, 2022 to 44.4 percent on Jan 9, 2022), the peak will likely be in the first half of February, the data suggests.
District Viral Graph Goes Viral
The State seems to be at its wit's end, as the viral graph goes viral in the State. From around 8.55 percent weekly positive rate during the period of Dec 31-Jan 6, the weekly positive rate (WPR) in Khordha has gone up to 13.07 percent during the period of Jan 3-9.
Similarly, for Sundargarh, the WPR has been up at 13.02 percent from 5.94 percent in the previous week, and in Sambalpur, the WPR jumped to 11.33 percent from around 3-4 percent.
It seems the districts of Khordha and Sambalpur are sitting on powder kegs. In the week ended on Jan 9, the RAT tests constitute a massive 61 and 76 percent, respectively.
The surge in weekly positivity rates in the districts, despite higher RAT proportion, underlines the explosive scenario in the districts. Because RAT tests detect one as positive only when the viral load is high. They cannot detect asymptomatic ones.
Odisha's RAT Plan A Red Carpet To Omicron?
The State today detected 28 new Omicron positives. The share of Omicron in genome sequencing in the State has risen to 14.5 percent today from 11 percent on Jan 6. The Omicron and its sub-lineages now garner 40 percent of the total genomes sequenced in the country, reveals the INSACOG data.
The Reason
As per a study published in MedRxiv, "The performance of Covid-19 diagnostic tests must continue to be reassessed with new variants of concern. Because, RAT confirms an Omicron infected individual as positive, only 3-days after RTPCR testing positive."
It further said, "We found that rapid antigen tests (RAT) lagged in the ability to detect Covid-19 during an early period of disease when most individuals were infectious with Omicron and four transmissions were confirmed. The median time from first positive PCR to first detectable antigen-positive was 3 days."
The study then further added that the policy implication is that rapid antigen tests may not be as fit-for-purpose in routine workplace screening to prevent the asymptomatic spread of Omicron, compared to previous variants, given the shorter time from exposure to infectiousness and the lower infectious doses sufficient for transmission."
The Key Takeaway
In agreement with the study done at a workplace in the US, the population-level Omicron epidemiology studies have earlier shown shorter serial intervals between cases and faster rates of community spread.
Since Odisha sends only around 5 percent of positive samples for whole genome sequencing (samples having a ct value of more than 25), the majority of asymptomatic cases were left out. This is the reason why the Omicron sample share in WGS (whole genome sequencing) is not dominant, but the rising share confirms the rapid-fire in covid cases is being triggered by Omicron in State hotspots.