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What may explain Delhi’s recent rise in COVID-19 cases?

3 September 2020

IDinsight’s Delhi COVID-19 Team.

3 September 2020

Delhi successfully managed the first wave of COVID-19 infections. But since early August, cases have been rising once again. Our team, which works closely with Delhi’s health department on COVID-19-related data management and policy, argues that the recent surge is largely driven by people not strictly following COVID-19 preventative behaviours, especially during festivals. Increased inter-state travel to Delhi, as the economy opens up, is also contributing to this increase. To curb this trend, we recommend a powerful and sweeping communications campaign on correctly wearing masks, maintaining physical distance, and following quarantine rules after inter-state travel.

Delhi had remarkable success in fighting the first wave of COVID-19, with its early focus on expanding hospital capacity to take care of critical patients, expansion of Rapid Antigen Testing near containment zones, and a robust home isolation policy that ensured that medical facilities could be used for more serious patients. Data from the Delhi government’s public-facing website and the state health bulletin suggests that the hospital bed occupancy never exceeded 60 per cent and the positivity rate, which had crossed 25 per cent in early June, stabilised around 5–7 per cent by mid-July. From a daily average of 3,300 cases during 23–28 June, Delhi dropped to 1,010 per day during the week of 27 July.

Delhi’s daily positive cases have been rising again, however, since early August. We’re back up to 1700 cases per day, with a positivity rate of 12 per cent (see Figures 1 and 2). The effective reproduction number,1 which remained below 1 throughout July, has now crept back up to 1.38.

Figure 1: Daily positive cases of COVID-19 in Delhi

Source: Delhi State Health Bulletin

Figure 2: Daily positivity rate (positive cases / total tests conducted) of COVID-19 in Delhi

Source: Delhi State Health Bulletin

Delhi’s seroprevalence surveys suggest that 30 per cent of the city has already contracted the virus, which means that the daily counts of patients who test positive for COVID-19 may be missing more than 95 per cent of actual infections. However, the occupancy percentages of hospital and ICU beds — which are arguably better metrics for tracking the severity of the virus’ spread in Delhi — are also trending upwards (see Figures 3 and 4). While some of this increase can be attributed to patients who have travelled from other states for Delhi’s more advanced medical facilities, it doesn’t fully explain the rise.

Figure 3: Occupancy and availability of COVID-19 beds in hospitals in Delhi

Source: Data reported by Nodal Officers of each Dedicated COVID-­19 hospital in Delhi, as per Delhi Fights Corona website

Figure 4: Occupancy and availability of COVID-19 beds in ICUs in Delhi

Source: Data reported by Nodal Officers of each Dedicated COVID-­19 hospital in Delhi, as per Delhi Fights Corona website
What could be behind this recent increase in COVID-19 transmission?

Based on conversations with district and state surveillance teams, as well as epidemiologists and public health experts, we developed six hypotheses to explain the recent rise. We evaluated these hypotheses based on available data, international and domestic trends, and feedback from state and district officials. Of the six hypotheses, we rule out two as contributing to the rise:

First, some have argued that given the high prevalence rates, it’s natural that as testing increases the number of detected cases will increase, even though the number of actual cases remains stable. However, we also see a rise in bed occupancy in hospitals, so increased testing alone does not account for the rise in cases. Further, we don’t find any correlation between the increase in cases and testing across Delhi’s districts.

Second, some argued that this increase may be an artefact of an increase in duplicate entries per patient or an increase in cases where patients are not in Delhi after they get tested. We find that the percentage of such cases over the past few weeks has remained fairly stable throughout July and August.

We discuss each of the remaining four explanations below:

  1. With the economy gradually opening up, Delhi residents have become complacent and let their masks down. There’s a lot more mobility for both work and leisure — which is needed to sustain economic activity — but insufficient precautions in terms of mask use, physical distancing, hand-washing, and other COVID-19 behaviours.
  2. The increased complacency was likely more acute during festivals in August, especially Raksha Bandhan, Eid ul-Adha, Janamashtmi, and Independence Day. We see increases in the daily case count a few days after each of these festivals. This is not conclusive evidence that festival gatherings, by themselves, have increased transmission. But accompanied by the general complacency, they seem to have contributed to the rise in cases.

Figure 5: Daily COVID-19 case counts in Delhi

Source: Delhi State Health Bulletin

3. Opening up has also led to increased inter-state travel. Some of this travel is because Delhi is a medical hub and people from all over India visit for treatment. For example, as COVID-19 has spread in neighbouring states, several COVID patients from these states, especially Uttar Pradesh, Bihar, and Rajasthan, have taken admission in Delhi’s hospitals. The proportion of COVID-19 patients from other states admitted to Delhi hospitals has increased by about 11 percentage points between the first week of July and the last week of August.

But in addition to medical reasons, people have also resumed travelling to Delhi for business, employment, and to meet relatives. Many migrant workers who left Delhi soon after the lockdown have also started to return. While these are positive signs for Delhi’s economic activity, it has probably contributed to higher infection numbers.

4. While Delhi has instituted a 7–14 day quarantine for those coming to Delhi using public transport, such isolation rules are not strictly being followed, especially among those travelling to Delhi using private road transport.

Since it’s highly likely that the recent surge in COVID-19 cases is driven by increased complacency and gaps in surveillance activities, particularly for people who have come from other states, the Delhi government needs to urgently take the following measures:

  • Increased communication regarding the importance of protective behaviours — especially wearing masks and physical distancing — can go a long way in saving lives. Delhiites might have grown immune to the existing messages, having heard them so many times now. But we can catch their attention again if we refresh the messages and the way we deliver them. Recognising this, the Chief Minister has reiterated the importance of wearing masks in his recent press conference. He also encouraged individuals to get tested if they have symptoms associated with COVID-19.
  • The Delhi government should re-advertise the existence of a supportive home isolation system for most patients who test positive for COVID-19. As part of Delhi’s home isolation model, most patients receive daily phone calls to check on them and free oxymeters to regularly monitor their blood oxygen levels.
  • The Delhi government needs to make shopkeepers and traders’ associations equal partners in this behaviour-change campaign. If they want the markets to remain open, they need to enforce protective behaviours in their markets. This can be checked through random inspections and testing by the government.
  • Increased surveillance, particularly for those who have travelled to Delhi from other states. Such individuals should quarantine themselves for 14 days and get tested in case they have any COVID or influenza-like symptoms. Delhi’s state and district surveillance system has already done a fantastic job in tracking COVID-19 positive patients and their contacts. Now the government needs to partner with local resident associations and hotels to ensure that they track those travelling from other states.

As Delhi continues to unlock, we’re working closely with the government to proactively respond to the recent increase in COVID-19 cases. The government rightly believes that actively tracking and managing this recent case growth will not only keep Delhi safe from COVID-19 but will also enable the economy to quickly return to track.

The views presented here are solely of the authors (IDinsight’s Delhi COVID-19 team) and do not represent the Delhi Government’s perspective. The graphs used in this article are produced as part of IDinsight’s weekly analytical bulletin for the government (reproduced here with the Delhi Government’s permission). This data is publicly available through the Delhi government’s Health Bulletin and the Delhi Fights Corona website.

  1. 1. The effective reproduction number is the average number of people in a population infected by an infected individual.