What Happened to COVID-19 Summer Wave?
The COVID-19 Summer Wave refers to the recurring increases in SARS-CoV-2 infections observed during the warmer months each year since the pandemic began. Driven by evolving variants, waning immunity, and increased social activities, these summer surges have become a predictable pattern, often alongside winter peaks. As of August 2026, a significant summer wave is underway across the United States, with infections rising nationwide, though severe outcomes like hospitalizations remain lower than in earlier pandemic years.
Quick Answer
COVID-19 summer waves have become an annual pattern since the pandemic's onset, characterized by increased infections during warmer months due to new variants, reduced immunity, and altered social behaviors. As of August 23, 2026, the United States is experiencing a widespread summer surge, with infections growing in nearly all states, particularly in the South and West. While overall activity remains low and hospitalization rates are significantly lower than previous peaks, public health officials continue to monitor the situation and recommend updated vaccinations and precautions for vulnerable populations.
📊Key Facts
📅Complete Timeline14 events
Initial Summer Rise in Europe
Despite initial perceptions of low cases, a rise in COVID-19 infections was observed across European countries, later attributed to underreporting due to limited testing.
Delta Variant Drives Summer Wave
The highly transmissible Delta variant became a dominant strain, contributing to a significant summer wave of infections globally.
Omicron Subvariants Fuel Summer Surge
Omicron subvariants, particularly BA.4 and BA.5, were responsible for a notable summer wave, demonstrating the virus's continued evolution and ability to cause off-season outbreaks.
End of US Public Health Emergency
The Biden administration officially ended the COVID-19 national and public health emergency declarations, shifting the pandemic response to a more endemic management phase.
The 'Hot COVID Summer'
A new surge in SARS-CoV-2 infections was observed, dubbed the 'hot COVID summer,' with Omicron subvariants like EG.5 remaining dominant. This wave was moderate compared to previous years.
FLiRT Variants Emerge, Global Surge
FLiRT variants began circulating, driving an increase in transmission and emergency department visits in the US. The WHO warned of a global surge, including at the Olympics.
WHO Warns of 'Worrying Comeback'
The WHO reported surging COVID-19 infections worldwide, with test positivity above 10% in many regions, and expressed concern about potentially more severe variants.
Summer Peaks Surpass Winter Peaks
Data from the CDC showed a summer surge with cases growing in at least 26 states. In California, summer peaks began to be higher than winter peaks, a trend noted by health officials. Nimbus and Stratus variants were circulating.
Cicada Variant (BA.3.2) Increases Detection
Reports of the BA.3.2 SARS-CoV-2 lineage, nicknamed 'Cicada,' increased, accompanied by greater detection in wastewater surveillance. This variant features significant genetic changes.
Start of 2026 Summer Wave
COVID-19 infections began to rise across the US, particularly in the South and West, marking the onset of the 2026 summer wave. Wastewater data showed increasing viral activity.
Infections Growing in All 50 States
According to the CDC's latest estimate, based on data through August 12, 2026, infections were growing or likely growing in all 50 states, indicating a widespread summer surge.
47 States Show Growing Infections
The CDC estimated that COVID-19 infections were growing or likely growing in 47 states, with no states showing a declining trend, confirming the nationwide spread of the summer wave.
Wastewater Surges 105% in August
Wastewater data reported a 105% surge in coronavirus concentrations in August compared to July, with the South and West leading the increase, signaling intensified transmission.
New XFG-Targeting Vaccine Expected
The updated COVID-19 vaccine, formulated to target the XFG variant (a dominant strain), is expected to be available for use beginning in the fall.
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🔍Deep Dive Analysis
Since the initial declaration of the COVID-19 pandemic in March 2020, the world has experienced recurring summer waves of SARS-CoV-2 infections, establishing a distinct seasonal pattern alongside traditional winter surges. The summer of 2020, initially perceived as having low case numbers, was later understood to have experienced significant underreporting due to limited testing capabilities, with a rise in infections noted across Europe. Subsequent summer waves in 2021 and 2022 were largely driven by the emergence of new, highly transmissible variants such as Delta and Omicron subvariants (e.g., BA.4/5), respectively, demonstrating the virus's continuous evolution.
The year 2023 marked a significant shift with the end of the federal COVID-19 public health emergency declarations in May. Despite this, the summer of 2023, dubbed the 'hot COVID summer,' saw a moderate surge in cases, primarily driven by Omicron subvariants like EG.5, indicating that the virus continued to circulate actively outside of emergency conditions. This trend solidified the understanding that COVID-19 would likely become an endemic virus with year-round activity, including predictable summer upticks.
The summer of 2024 witnessed a global surge in infections, with the World Health Organization (WHO) expressing concerns about a 'worrying comeback' and the potential for more severe variants. In the U.S., FLiRT variants were identified as key drivers, leading to increased transmission and emergency department visits, with wastewater surveillance showing high viral activity in many states. This pattern continued into the summer of 2025, where, particularly in regions like California, summer peaks began to surpass winter peaks in terms of case numbers, with new variants like Nimbus and Stratus circulating.
As of August 23, 2026, the United States is in the midst of another significant summer wave. The Centers for Disease Control and Prevention (CDC) estimates that COVID-19 infections are growing or likely growing in nearly all 50 states, with particular increases noted in the South and West. Wastewater data, a crucial early indicator, shows substantial increases in SARS-CoV-2 concentrations, with some reports indicating a 105% surge in August compared to July. Dominant variants include 'Nimbus' (NB.1.8.1) and 'Stratus' (XFG), along with the 'Cicada' (BA.3.2) variant, which carries significant genetic changes that may impact vaccine effectiveness.
While transmission is widespread, national hospitalization peaks have continued to decline since the 2023-2024 winter, and emergency department visits remain 'very low' nationally. This reduced severity is attributed to greater population immunity from prior infections and vaccinations, as well as potentially less severe dominant variants. Public health guidance for 2026 emphasizes continued vigilance, recommending updated COVID-19 vaccines (with the 2026-2027 vaccine targeting an XFG strain expected in the fall), staying home when sick, and considering masks in crowded indoor spaces, especially for older adults and immunocompromised individuals.
What If...?
Explore alternate histories. What if COVID-19 Summer Wave made different choices?