COVID Update- LP.8.1’s Rapid Growth and Its Impact on the U.S. This Winter and Spring. An Overview of What Else is Spreading
U.S. Wastewater Testing of Multiple Viruses
COVID-19 cases are surging in the Northeast and Midwest, while the rest of the U.S. appears to have peaked around December 30th. It is very likely that prevalence will start declining in the wastewater in the Northeast and Midwest within the next week. Due to reporting delays—from sample collection to testing and data release—this decline may already be underway but isn’t yet visible in the current data.
In addition to COVID-19, the Northeast is experiencing sharp increases in RSV and Influenza A cases. Norovirus has been more widespread in the Northeast but seems to have peaked nationally, with slight declines now appearing across the country. Meanwhile, Enterovirus D68 (EVD68) is also rising in the Northeast.
This raises an important question: How much influence might the XEC variant and/or LP.8.1 be having on these trends? COVID-19 weakens the immune system, potentially paving the way for spikes in other infections. Could one of these variants be driving the surge of other viruses in the Northeast? It’s certainly a possibility worth exploring.
We’ll also explore why LP.8.1 and its descendants are likely to maintain a growth trajectory—unless a new variant emerges that can out-compete it.
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Test Positivity Rates Show Similar Trend to Wastewater Testing
Data from Walgreens and the CDC show that COVID-19 positivity rates began declining after December 30, 2024, following a similar pattern seen in previous years. It’s important to remember that symptoms typically appear a few days after exposure. That suggests that all the people who were exposed over the holiday travel season and at family and friends events was less then the exponential growth between schools and homes which was cut off when children went on school break. As a result, both Influenza A and COVID-19 rates began to decline across most of the country by December 30th.
U.S. Variant Proportions
We can see below that the XEC variant continues to expand but due to the time of year and the overall decrease in cases that is expected due to the school break, its time in the limelight is limited. We have a new contender that will soon overtake it. Had LP.8.1, which we will discuss shortly, had gained traction earlier then we likely would have had a much larger surge this December. In large part to the fact that the KP.3.1.1 surge was so large over the summer and sustained itself for so long while the exponential growth was occurring we did not have a large surge this December.
CDC variant data shows XEC variant has grown to about 45% of all cases. The XEC variant hasn’t been able to cause as many infections this December as was anticipated. The earlier surge of KP.3.1.1 over the summer appears to have provided a solid immune response that protected people from the XEC variant. Anyone infected over three months ago will begin to get more vulnerable to a new infection.
The next variant we are watching closesly is the LP.8.1 variant. LP.8.1 has steadily increased from 2% to 4% and now to 8% over the past three reporting periods (spanning six weeks). If this trend continues, LP.8.1 could rise to 16% in two weeks, 32% in four weeks, and 64% in six weeks. This rapid growth suggests the potential for a larger-than-usual late winter and spring surge, possibly lasting through mid-April.
But why might this surge taper off in mid-April? Share your thoughts in the comments below.
Virological and antigenic characteristics of SARS-CoV-2 variants LF.7.2.1, NP.1, and LP.8.1
A pre-print study published on December 27, 2024, examined the virological and antigenic properties of several COVID-19 variants. The findings suggest that LP.8.1 is likely to outcompete the XEC variant. The study states, "Most importantly, we found that LP.8.1 showed comparable humoral immune evasion to XEC but demonstrated much increased ACE2 engagement efficiency, supporting its rapid growth." This means LP.8.1 can infect cells more easily, giving it a significant advantage.
The graphic below highlights that LP.8.1 has the strongest growth advantage compared to other circulating variants.
LP.8.1 is Increasing Across Multiple States in Early December
The graphic below, posted on X by Mike Honey, shows the growth of LP.8.1 through December 2, 2024 in the states it showed up earliest. It’s interesting to note that New Jersey, Rhode Island, and New York are showing rising positivity rates according to the Walgreens Respiratory Index. In contrast, states like California, Colorado, and Minnesota aren’t seeing the same increase—likely due to the overall decline in cases. This early trend supports the idea that LP.8.1 may be driving a larger surge in the Northeast, where colder temperatures have been keeping people indoors with reduced ventilation, creating conditions that facilitate virus spread.
TACT’s Overview
Although LP.8.1 is steadily displacing other variants, overall COVID-19 prevalence is expected to decline for at least several weeks. However, with the end of the holiday break, the cycle of exponential transmission between schools and homes has resumed. It will take 1 to 2 months to see it in the data, but it is occurring. As LP.8.1 spreads through schools, it will continue moving into households, workplaces, and communities, expanding its reach.
It’s still too early to determine the full impact of this variant, but infections will occur—and LP.8.1 may temporarily weaken immune systems, increasing vulnerability to other viruses and bacterial infections.
Prioritizing improvements in air filtration and ventilation in schools would play a critical role in reducing the overall burden of illness across the U.S. and globally. We must work Together Against COVID Transmission.
Share your thoughts, questions or insights.
Thank you. In Minnesota- our hospitals haven’t been this bad since 2020.
23 people have died from the flu.
I really think that people have immune system damage and can’t fight off flu, rsv, covid, and norovirus. In the Minnesota reddit, so many people are writing about their entire family being sick. 🤢
My household hasn’t gotten sick. My spouse passed on some high exposure activities, my son is wearing his mask, as am I. And, I don’t share air outside of my household when the hospitals are full.
I disagree with this title- unprecedented flu. It was completely predictable.
https://bringmethenews.com/minnesota-news/unprecedented-flu-spike-hitting-minnesota-data-shows
TACT...As if you don't have enough pathogens to watch, Human Metapneumovirus (hMPV) might be another one to keep an eye on. While commentators often mention its mildness, there does appear to be some genetic evolution ongoing. Where this all leads is unclear at this point, but I'm not sanguine about its continued "mildness".
https://www.news-medical.net/news/20250106/Novel-hMPV-strains-linked-to-rising-respiratory-infections-in-young-children.aspx