According to experts, even in the case of Omicron causing mild symptoms, its infection rate is still likely to cause an increase in hospital admissions.
Just three weeks since it was discovered, Omicron has shown an amazing growth rate. The World Health Organization (WHO) on December 12 warned that the strain has an infectious advantage over Delta, making it easy to become a dominant strain in places where it is circulating.
However, Omicron seems to cause milder clinical symptoms. In South Africa, where the mutation first appeared, the number of people who transferred was small. To date, the world has only had one death from mutation, recorded in the UK. Of the more than 4,700 infections in the country, only 10 patients have been hospitalized. All 1,686 cases of Omicron in the European Union were mild or asymptomatic.
However, scientists warn it is too early to conclude Omicron is not dangerous. The number of infections is still low, data is limited, and the impact of mutations on the global population is not fully demonstrated.
Even in a confirmed case causing milder symptoms, Omicron remains a threat because of its infectious speed. Associate Professor Ian Mackay, a virologist at the University of Queensland in Australia, said Omicrons are so effective that they can overwhelm Delta where they co-circulate. In South Africa, unvaccinated people still need to breathe oxygen.
“Although the virus does not cause severe or dangerous illness, it still causes many people to be hospitalized. We need to remember that a small percentage of highly contagious infections can still create a large epidemic,” said Mr. Mackay.
South Africa’s overall daily number of nCoV infections rose to 18,000 on December 12, much higher than the more than 1,200 at the end of November, when the mutation was first reported.
The virus’s R0 infectivity coefficient (the number of people who can get nCoV from an F0) is currently 2.5, higher than at any time during the pandemic. According to South Africa’s Ministry of Health, the increasing hospitalization rate may be due to the higher total number of people infected with Covid-19.
Meanwhile, the number of Omicron infections doubles every two to three days in the UK. The country’s Health Security Agency predicts it will soon become the dominant strain. Without restrictions, the number of Omicron cases will rise to 200,000 a day by the end of December, hospitalizations could double in the next two weeks. Therefore, the British government urges people to vaccinate to strengthen immunity against new strains.
Denmark experienced a similar situation. The number of Omicron cases doubles every two days. The Statens Serum Institute estimates it will become the dominant strain this week, increasing pressure on the health system.
It is not clear why Omicrons transmit so efficiently. Scientists think the reason lies in mutations in the spike protein on the outside of the virus envelope. They both increase the ability to adhere to host cells and help the virus escape immunity.
Many studies show that Omicron can reduce the effectiveness of vaccines. Experts have recorded a number of breakthrough infections in people who have received two full doses of the vaccine and also a booster dose.
Kwok Kin-on, a professor of epidemiology from the University of Hong Kong, said careful study of the severity data of recent infections was needed. Especially when Omicron is three to eight times more likely to cause reinfection than Delta. According to Professor Kwok, the strain with a high rate of reinfection will lead to many cases of mild symptoms.
Professor Michael Plank, Cambridge University School of Mathematics and Statistics, an expert in epidemiological modeling, warned that the world is facing a pathogen that spreads faster than Delta.
“It can make a lot of people sick. Given the high number of people infected with nCoV, even a small hospitalization rate is enough to cause serious problems for a health system that is already under pressure because of Delta,” he said. speak.
Scientists are still in the process of answering three big questions: How effectively Omicrons spread, how immune-evading, and how virulent it is to cause severe disease. Peter Chin-Hong, a professor of infectious diseases at the University of California San Francisco, said preliminary data on Omicrons in South Africa should be interpreted with caution.
In South Africa, the average age is around 27. According to some estimates, maybe 60-80% of the adult population in this country has been infected with nCoV. This is likely the reason that the initial positive cases reported were all mildly symptomatic.
“South Africa is very different from the rest of the world. The country has a young population. Apart from HIV, people usually don’t have other immunodeficiency or underlying diseases like the US. The country is affected. severely affected by consecutive Covid-19 waves, so significant immunity may have been reached,” Professor Chin-Hong said.
In contrast, many countries that experience fewer outbreaks, have aging populations, and many immunocompromised people are more vulnerable to Omicrons.
Professor Kwok cautions that more data is needed to fully understand Omicron’s impact on different age groups. “It is three to four weeks until the number of infections and deaths becomes clear. The good news is that we have not recorded too many deaths, but still have to wait a week or two to see if the mortality rate stabilizes or not. “, said Mr. Kwok.
Thuc Linh (Follow SCMP)