The occupancy rate of hospital beds for COVID-19 patients in serious condition in Tokyo has reached the most severe stage, and scientists warn that the situation could rapidly worsen in the coming weeks.

The occupancy rate hit 52 percent, putting that category in gauging the infection spread at stage 4 of a four-level alert under the central government’s standards.

Tokyo is also at stage 4 in terms of the number of daily new COVID-19 cases, hospitalizations, infected people with nonserious symptoms recuperating at hotels and homes, and the rate of positive tests for the virus, data by the metropolitan government showed.

About 2,400 patients with COVID-19 are now hospitalized in the metropolis.

The number of patients staying at home because they did not have access to hospital care or because they had mild symptoms soared to 3,657 on July 20, compared with 1,841 a week earlier.

If the spread of novel coronavirus infections in Tokyo accelerates from the current pace, the capital will sink into a “crisis” situation in less than two weeks, health experts warned.

That future scenario could prove more daunting than the record-setting wave of infections in winter, they said.

A big concern in the latest increase is that the highly transmissible and potentially more deadly Delta variant has rapidly replaced other strains, they added.

A rolling seven-day average of new infections over the week until July 20 was 1,170, up by 49 percent from 785 for the preceding week.

A month ago, the seven-day average to June 21 was 387 new cases.

The numbers indicate the novel coronavirus is now sweeping through Tokyo faster than when it pounded the capital in the third wave of infections between late 2020 and early 2021.

If the pace continues at the current level, the seven-day average of new infections would reach an estimated 1,743 on July 27 and 2,598 on Aug. 3, health experts said.

“The prediction for Aug. 3 would far exceed the peak seven-day average of 1,816 during the third wave of infections,” one of the experts said.

The metropolitan government reported 1,832 new cases on July 21, the first time since Jan. 16 for the single-day count to top 1,800.

But the official figure for newly confirmed infections in Tokyo may reflect only a fraction of the actual number.

In a metropolis with 14 million people, the new COVID-19 cases are recorded from a limited number of tests for the virus.

Data from the metropolitan government showed that the three-day average of PCR tests conducted until July 20 was 8,206.

Perhaps more telling is that the seven-day average rate of positive results from the PCR tests rose to 10.2 percent as of July 20, up from 7.2 percent for the previous week.

The Delta variant accounted for 30.5 percent of the new cases in Tokyo over the week through July 11, according to metropolitan government data. The ratio was 21.5 percent in the previous week.

Statistics for the variant are not immediately available because genome sequencing to detect the strain takes time.

“We should remain alert about the Delta variant,” a health expert said.

Metropolitan government officials reported that crowd sizes in entertainment districts in Tokyo have shrunk slightly since the capital was placed under the fourth state of emergency from July 12.

They underscored the need for Tokyo residents to stay home during the four consecutive holidays that began on July 22 to host the Olympic Games.

Hiroshi Nishiura, professor of infectious disease epidemiology at Kyoto University, gave a grim prediction at a July 21 meeting of the health ministry’s expert panel on the coronavirus if measures are not taken to minimize the risk of spreading the contagion.

He said the number of hospitalized COVID-19 patients in Tokyo could surpass 3,000 in mid-August if the effective reproduction number, or the number of secondary cases caused by one infected person, drops only by 10 percent from the current 1.2.

He also said that without improvements in this category, serious cases of COVID-19 will sharply rise.

The share of seriously ill patients in their 40s and 50s needing hospital treatment would soar because that age group was given lower priority in the vaccination program, and relatively few of them have been fully inoculated, Nishiura said.

On July 22, the metropolitan government was expected to start services at Heisei Tateishi Hospital in Katsushika Ward for people who are battling COVID-19 but have no access to medical care.

They can receive oxygen and medications while undergoing other examinations, including electrocardiograms and tests for their blood-oxygen saturation level, an indicator of their lung condition.

The service is intended to help patients who cannot find hospital beds because they are rapidly filled up with COVID-19 patients.

(This article was written by Momoko Ikegami, Yoshitaka Unezawa, Kai Ichino, Yuki Edamatsu and Naoyuki Himeno.)