CNA Explains: The FLiRT family of COVID-19 variants and what we know about the KP.2 strain

ARE THE NEW STRAINS MORE INFECTIOUS?

The US CDC said on May 16 that while KP.2 is the main variant, it isn’t causing more severe illness than other variants.

Singapore’s Health Ministry similarly said on May 18 that there are currently no indications that KP.1 and KP.2 are more transmissible or cause more severe disease than other circulating variants.

But slight differences in KP.2’s spike protein might make it better at evading our immune defences and slightly more infectious than JN.1, according to Dr David Ho, a virologist at Columbia University who was quoted by the New York Times.

It could even infect people who received the most updated vaccine, Dr Ho added, since that shot targets XBB.1.5, a variant that is different from JN.1.

“They certainly can evade the immunity conferred by the earlier vaccinations … or earlier infections before JN.1,” said Dr Leong Hoe Nam, an infectious diseases expert at Rophi Clinic in Singapore.

He was referring to earlier versions of COVID-19 vaccines such as the bivalent ones.

DO KP.1 AND KP.2 CAUSE MORE SEVERE SYMPTOMS?

The symptoms for KP.1 and KP.2 are the same as earlier variants, Dr Leong said, adding that there is no indication the variants lead to more severe illness.

In fact, said Professor Paul Tambyah who cited the Infectious Diseases Society of America, disease caused by KP.2 and KP.1 is less severe than their ancestor JN.1. 

However, KP.2 and KP.1 may be more transmissible, said Prof Tambyah, who is the president of the International Society for Infectious Diseases. Their behaviour follows that of all viruses, which eventually evolve to become more transmissible and less virulent.

“Even the deadly 1918 influenza pandemic virus, which killed one in 50 people worldwide, simply evolved to become the dominant strain of seasonal influenza from 1920 to 1957,” noted Prof Tambyah.

Like JN.1 and previous Omicron variants, it may take five or more days before a person starts to develop symptoms after exposure, although symptoms may appear sooner, said Professor Andy Pekosz from the John Hopkins Bloomberg School of Public Health.

“When it comes to symptoms, we’re not seeing anything new or different with these variants,” he added.

“We continue to see more mild disease, but that’s likely not because the virus is milder, but because our immunity is so much stronger now.”

Symptoms include fever, sore throat, runny nose and fatigue.

Fewer people lose their sense of taste and smell now than they did at the start of the pandemic, but some may still experience those symptoms.

Infected people could also experience gastrointestinal symptoms like diarrhoea, nausea and vomiting, which are sometimes confused with norovirus symptoms.