Another outbreak? Karnataka's Covid-19 reproduction rate crosses 1

Karnataka’s effective reproduction rate (Rt) of the novel coronavirus has crossed 1, indicating the beginning of another outbreak. According to epidemiologists and analysis run by the University of Michigan, the state’s effective R number is currently 1.13. If the Rt exceeds 1, each existing infection will cause more than one new infection, leading to an outbreak.

In Karnataka, there has been a 15.4% increase in the number of new cases in the last seven days. In Bengaluru Urban, cases have increased by 8.7%, but municipal officials are watching the situation carefully.

New numbers being projected by mathematical models are discomfiting. The University of Michigan’s projections say that Karnataka will add at least 28,700-odd new cases in the next 29 days. However, the group’s “upper confidence interval” projections suggest several lakh cases.

The BBMP war room has been conducting AI-based modelling, which is cross-referenced with third waves in countries like the UK, Japan and Indonesia.

They have been coming up with some disturbing numbers: between 10-15,000 cases daily in the city once a surge begins. “At the same time, hospitalisations will be brief because clinical outcomes are expected to be better,” a BBMP source said.

Also read: 'Restrictions in place in Karnataka till Covid-19 positivity rate comes down'

Of the rising cases, D Randeep, Special Commissioner (Health), BBMP, said they are due to the further opening up of the economy. “At the same time, I do not think it is the beginning of the third wave,” he added.

Echoing the views, epidemiologist Dr Giridhar Babu said, it is too early to determine if this is the beginning of a new wave. “These are early signals. The rising RT today, will show cases later. Naming the second or third wave is purely semantic in nature. Technically, there has to be an intermittent period of lower levels of transmission, after some time which cases will increase,” he said.

However, he cautioned that districts or areas with low vaccination coverage and low seroprevalence will have higher cases, higher need for hospitalisation and more deaths. This uncertainty has in part, prompted municipal authorities in Bengaluru to kick-start a four-day serosurvey on Wednesday, covering about 2,000 people to determine where the city stands in terms of seroprevalence.

In DJ Halli ward, for example, there has not been a single case in the last seven days. “Bommanahalli has one of the largest numbers of containment zones. We want to find out why,” Randeep said. There are 1,919 households in 27 containment zones in the Bommanahalli zone.

Hospitalisation rising

At Manipal Hospital on HAL Airport Road, more Covid-19 patients have started to filter in. Among them are people who had been vaccinated in June coming in with breakthrough infections. “But their case severity is not high. The bulk do not require respiratory support,” explained Dr Anoop Amarnath, an expert in geriatric care and a member of the State’s Critical Care Support Unit (CCSU).

According to Manipal, the hospital had 37 new ICU patients in July, of which only two were fully vaccinated. “Data suggests that the risk of death is less than 0.5% in vaccinated people,” the hospital said.

In Bengaluru Urban, 75% of the target adult population has been vaccinated while nearly 20% have the second dose.