Omicron symptoms like catching a cold, HKU researchers find

Omicron seems considerably less severe than previous Covid strains with cold-like symptoms including mild fever and scratchy throat, with many vaccinated patients showing no symptoms.

Other symptoms include extreme body pain, night sweats, vomiting and loss of appetite.

According to experts, the Omicron variant is said to have a high infectivity rate. But preliminary studies have shown that the new variant is considerably mild.

A University of Hong Kong research team led by chair professor of Department of Microbiology Yuen Kwok-yung found that the Omicron variant is less effective in replicating cells and causing diseases than other Covid-19 variants.

Looking into Omicron's replication efficacy and pathogenicity in a series of cell and mouse models, the team found that replication of the live Omicron virus was reduced compared to the original strain, as well as the Alpha, Beta and Delta variants.

Omicron is also more than three times less efficient at viral multiplication compared to the original Covid-19 strain in human lung epithelial cells.

Researchers said the study suggested that the current global vaccination strategy has forced the Covid-19 virus into a new evolutionary trajectory towards lower replication fitness in exchange for better immune escape.

"This development implies that vaccination including additional boosters may drive further attenuation of the virus," the team said.

Respiratory expert Leung Chi-chiu said the symptoms for those infected with Omicron could be more mild than other variants if the patients were young and had no chronic illnesses.

This means that these patients are less likely to undergo hospitalization or be admitted to intensive care units. "One of the main reasons [for the mild symptoms] could be the results of natural infections or vaccination which offers partial immunity to the patients," he said.

He was citing figures from the United States and South Africa, which showed that the number of vaccinated patients developing serious symptoms were fewer than those who were not vaccinated.

"While the impact of the virus itself might have lowered, this seems to be a more minor reason," he said.

He added that the public should stay vigilant as there were still people infected with Omicron who had serious symptoms or needed to be under intensive care.

Leung also said Hong Kong must continue its dynamic zero-Covid policy, which helped buy time to increase the overall vaccination rate given that the vaccination rate of elderly aged 80 or above was still below 30 percent.

"If we can achieve zero-Covid, then we can consider opening the border with places that use the same strategy such as the mainland," he said.

A Hongkonger surnamed Chan who moved to the United Kingdom in June last year, said all three members of his household were infected but the UK authorities only asked them to undergo home quarantine for 10 days and only to seek help if their situations deteriorated.

After the 10 days, Chan said his entire family had recovered without any medication, even though their six-year-old daughter had a fever for three to four days, while Chan and his wife lost their appetites and felt tired.

"After my recovery, I honestly think it was just the flu but the Hong Kong government takes it so seriously and imposed lockdown when someone was infected.

"It should learn the approach of living with the virus so citizens can live a normal life," he said.

The World Health Organization said vaccination was expected to provide important protection against severe disease and death caused by Omicron, as it did with the other variants still in circulation.

"The comparatively lower rate of hospitalizations and deaths so far is in large part thanks to vaccination, particularly of vulnerable groups," it said.