US health authorities do not currently consider the Mu coronavirus mutation -- the latest “variant of interest” -- to be a threat, Dr Anthony Fauci said during a White House Covid-19 Task Force briefing on Thursday.
The World Health Organisation announced on Tuesday it is investigating the new Covid-19 strain, first discovered in Colombia this year.
The variant is now Colombia's predominant strain and was behind its deadliest pandemic wave yet, between April and June, health official Marcela Mercado told a local radio station.
Mu “has a constellation of mutations that indicate potential properties of immune escape", the WHO said.
“We're certainly aware of the new variant,” Dr Fauci said. “We're keeping a very close eye on it.”
Asked if the US is taking any steps to deal with a possible outbreak of the Mu variant, he said vaccination is currently the best precaution.
“Remember, even when you have variants that do diminish somewhat the efficacy of a vaccine, the vaccines still are quite effective against variants of that type,” he stated.
New coronavirus strains are added to the WHO's “variant of interest” list before being elevated to “variant of concern” status. The highly transmissible Delta variant was named a “variant of concern” this year.
“There have been sequences here but over 99 per cent of sequences we're seeing here are the Delta variant,” Centres for Disease Control and Prevention (CDC) Director Dr Rochelle Walensky said.
“We don't consider [it to be] an immediate threat at this time,” Dr Fauci added.
The country is experiencing a serious surge in infections, with a seven-day average of more than 150,000 daily cases and 1,046 deaths due to the spread of the Delta variant in areas with low levels of vaccinations.
The US is also reporting a concerning increase in child hospital admissions as the school year begins.
“Our children's healthcare safety net is under unprecedented strain,” Children's Hospital Association chief executive Mark Wietecha said in a statement on Monday.
On the behalf of more than 220 children's hospitals, Mr Wietecha begged Washington for help.
Most children suffer only mild symptoms of Covid-19, but it is unclear if the Delta variant affects them more.
“In August 2021, the rate of hospitalisation for children was nearly four times higher in states with the lowest overall vaccination coverage,” Dr Walensky said.
People under the age of 12 are not yet eligible to be vaccinated against Covid-19 in the US.
Only 61.7 per cent of the vaccine-eligible population has been fully vaccinated.