Early third wave data from Mumbai: Severity low, oxygen needs low, but puzzling hospitalisation rate

Mumbai is among the cities where India’s third wave of Covid-19 first became noticeable.

The first case of Omicron was detected in the larger Mumbai Metropolitan Region on December 4 when a 33-year-old resident, who returned from South Africa, tested positive for the new, highly infectious variant of the coronavirus.

Ten days later, Mumbai started witnessing a surge in Covid-19 cases. From 1,797 cases on December 15, the active caseload in the city rose to 37,274 on January 4 – a 20-fold jump in 20 days.

Since the early trends in Mumbai could offer a glimpse of what India’s third wave may look like, Scroll.in closely examined the Brihanmumbai Municipal Corporation’s data on Covid-19 cases.

Hospitalisations

Between December 15 and January 4, municipal data shows the number of Covid patients hospitalised in Mumbai rose five times from 916 to 4,491, those admitted to intensive care units doubled from 254 to 507 and those requiring oxygen support rose from 384 to 1,374.

While the daily infections in Mumbai have increased rapidly since December 15, the increase in hospitalisation has been slower and admission to intensive care units even slower.

Currently, according to the civic body’s data, 13.2% of the total infected cases in Mumbai are admitted to hospitals. The number is surprising given that municipal data also shows that of the active cases in the city, 90% are asymptomatic or have mild symptoms, 9% are moderately symptomatic and stable, and less than 1% are critical. If only 10% of the active cases have more than mild symptoms, then why are 13.2% of the cases in hospital?

Municipal officials attributed this to an affluent section of society preferring hospital admission out of caution and to access monoclonal antibody cocktail therapy. Private hospital admissions currently account for 36.6% of overall Covid-related admissions in the city. (More on this later.)

Severity of disease

Of the Covid patients currently hospitalised in Mumbai, at least 18% have severe disease – 11.2% are in intensive care units and 7% on ventilator support.

Apart from those admitted to intensive care units and on ventilator support, according to doctors, severe patients include those with lung impairment that requires high oxygen support. But not all patients on oxygen support are considered severe. Of the patients currently hospitalised in Mumbai, 30% require oxygen support.

Dr Rahul Pandit, intensivist at Fortis Hospital and member of the Maharashtra Covid-19 Taskforce, said a clear decline is visible in the proportion of patients requiring oxygen support. During the second wave of Covid-19 in the summer of 2021, which was fuelled by the Delta variant of the coronavirus, 85-90% of patients getting hospitalised required oxygen support – three times the current number.

Even the amount of oxygen required per patient is lower. “Early trends show even in ICU, patients need two to four litres of oxygen per minute. During the second wave, they required 10-20 litres per minute,” Pandit said.

Dr Akash Khobragade, superintendent at St George’s Hospital, said the Omicron variant is not infecting the lower respiratory tract as badly as the Delta variant did, thus reducing the need for oxygen support.

Bed occupancy

What worries civic officials is that even if the rate of hospital admissions is lower compared to the second wave, the Omicron variant is expected to cause an explosion in cases which may lead to a rise in admissions in absolute numbers, putting a burden on critical health infrastructure for a few days or weeks.

Virologist Dr Shahid Jameel said the Omicron variant, which is highly transmissible and spreads faster than the Delta variant, will lead to a higher caseload than previous waves.

Since December 15, daily hospital admissions in Mumbai have risen from 50-60 per day to over 800.

Between December 15 to January 4, hospital bed occupancy rose from 5.9% to 14.1%, intensive care unit bed occupancy rose from 12.7% to 20% and ventilator occupancy increased from 14.6% to 23%.

This is despite the fact that the Brihanmumbai Municipal Corporation scaled up its intensive care unit beds from 1,985 to 2,577, and ventilators from 1,156 to 1,368 in the same period.

Occupancy of oxygen beds increased from 5.6% to 11.4%, even as more than 5,000 oxygen beds were added after December 15.

A different trajectory

Since hospitalisations usually lag by a week or two, it might be early to predict the trajectory of hospitalisations and severe cases based on the current data. It is, however, noteworthy that Mumbai’s hospitalisation rate is higher than Gauteng province in South Africa where the Omicron variant was first detected.

Gauteng reported a quick surge and fall in cases over November and December. Data for the first four weeks of the Omicron-led wave, yet to be peer-reviewed, was published in The Lancet on December 29. It showed the hospitalisation rate – the percentage of cases admitted to hospitals out of the total number of reported infections – stood at 4.9%, down from 13.7% in the previous Delta-led wave in the province.

The study stated that of those hospitalised in Gauteng, 28.8% had severe illness in the latest wave, compared to 66.9% in the previous Delta-led wave. The study counted severe patients as one or more symptoms of acute respiratory distress, supplemental oxygen, mechanical ventilation, high and intensive care or death as severe infection.

South Africa’s vaccination coverage stood between 25-30% during the Omicron wave. Mumbai’s current full immunisation coverage is nearly 40% of total population, which should ideally put it in a relatively better position, reducing the incidence of severe disease, say experts. “Looking at all these factors, it seems Delhi and Mumbai will also follow a similar trajectory as Gauteng,” said public health expert Dr Chandrakant Lahariya.

But not only is the hospitalisation rate in Mumbai higher than in Gauteng in South Africa, it is also significantly higher than Delhi, which is also witnessing a surge in Covid-19 cases. In the capital, of 14,889 active cases, 531 are hospitalised, accounting for 3.5% of total infections, much lower than Mumbai.

Another city where cases have exploded is Kolkata, which currently has 12,739 active cases. While the state government does not publicly share separate hospitalisation data for the city, West Bengal has a 7% hospitalisation rate.

Affluent patients demand antibody cocktail

In Mumbai, civil officials say the city’s hospitalisation rate is higher because of an affluent section of society preferring admission out of caution. “If we start checking data for private hospitals, we will find a lot of asymptomatic or mildly symptomatic patients are admitted who really don’t require hospitalisation,” said Dr Mangala Gomare, Brihanmumbai Municipal Corporation’s executive health officer.

Mumbai has 4,414 private beds available across 94 hospitals. Of these, 1,645 or 37% are full.

What could also be skewing the hospitalisation rate is the demand for the monoclonal antibody cocktail therapy, in which artifically synthesised antibodies are infused in a patient to help their immune system fights off infection. Evidence suggests it is not as effective against Omicron as it was against Delta.

Despite that, many affluent residents in Mumbai, who have tested positive for Covid-19 and don’t otherwise require hospital care, are getting admitted in private hospitals for the antibody cocktail. Civic officials said a majority of those testing positive are from residential buildings and high-rises. “This is also the section that can afford private treatment,” a medical officer said.

Dr V Ravishankar, chief operating officer in Lilavati hospital, said patients continue to demand the monoclonal antibody treatment. “I have patients waiting outside our patient department for this. It takes about four hours to administer this to one patient. We are treating most on a daycare basis,” he said.

Said Dr Pandit from Fortis Hospital: “Considering the rampant spread of Omicron in the city, I have reduced use of this cocktail for my patients.”

But several intensivists in Mumbai said they have to bend to the patient-driven demand for the antibody cocktail. “Some patients insist on being administered this,” said Dr Gautam Bhansali, consultant physician in Bombay Hospital. Bhansali said many patients currently seeking admission in private hospitals are there for the monoclonal antibody cocktail. “And they are discharged within 2-4 days,” he said.

In government hospitals, admission is more controlled. Dr Hemant Deshmukh, who retired as dean at KEM hospital last week, said he had been only admitting patients who fit the criteria for admission. “We give monoclonal antibody based on protocol to those aged over 50 years and have a risk of progression into severe infection,” he said.

The detection of positive cases is currently limited to high rises and middle-class residential societies. According to the municipal corporation’s data, there are 16 containment zones in slums and chawls, compared to 389 sealed residential buildings. At least 5,522 floors in buildings are sealed. The number of sealed buildings is an indication of high infection spread in housing societies.

No major change in affected age group

In terms of age, those between 30-39 years followed by 20-29 continue to form the biggest chunk of cases in Mumbai.

An analysis by Scroll.in of the 40,000 fresh cases detected in the last few days shows 8,560 people belong to the 30-39 age group and 8,344 to the 20-29 age group. This was followed by 6,658 people in the 40-49 age group. Those aged between 20-50 continue to be the most affected as they step out for work.

Data on the age profile of the hospitalised cases could not be accessed from the municipal corporation. Dr Gomare, the civic body’s executive health officer, however, said most of those in hospital are the elderly with comorbidities.

Out of 40,000 cases, over 4,000 were aged less than 20 years, accounting for 10% of total infections. Civic officials said they do not observe a major change in the age pattern of those getting infected before and after Omicron started circulating in the city.

While those aged 18 and lower were not eligible for vaccination before January 3, it has not increased their infection numbers in proportion to total cases due to the Omicron variant yet.

This reporting was supported by a grant from the Thakur Family Foundation. Thakur Family Foundation has not exercised any editorial control over the contents of this article.