COVID rises again in summer: why surges return even outside the winter season and who should be more careful
COVID-19 has long ceased to be an exclusively winter infection. In some countries, a rise in SARS-CoV-2 circulation is again being recorded in summer, although globally virus activity remains comparatively low. According to the World Health Organization, by mid-July the share of positive SARS-CoV-2 tests rose to about 4% after a record low of around 1.2% in May.
At the same time, WHO emphasizes: this is not a new global wave on the scale of the first years of the pandemic. Increased activity is observed locally and varies across regions.
Key points about the summer COVID-19 situation:
- Local rise: The virus does not have clear seasonality; summer surges are linked to mass travel and long stays in air-conditioned spaces with closed windows.
- New indicators: Given the reduction in mass testing, wastewater monitoring has become the main early signal of rising incidence.
- Risk groups: The global threat is assessed as moderate, but for elderly people and patients with chronic diseases the risk of severe illness remains high.
Why COVID can rise even in summer
Unlike influenza, SARS-CoV-2 has not yet developed clear seasonality. It can spread actively in both winter and summer. One reason for summer surges is changes in people's behavior.
In hot weather, people in many countries spend more time in air-conditioned indoor spaces where windows are closed and ventilation is limited. In summer, the number of trips, flights, mass events, festivals, and family gatherings also sharply increases. All this increases the number of close contacts between people from different regions.
Immunity wanes over time
Another factor is the gradual weakening of protection after previous infection or vaccination. Immunity against severe disease lasts longer than protection against infection itself. Therefore, a person who has been infected or vaccinated several months ago can still become infected again.
An additional role is played by the constant evolution of the virus. SARS-CoV-2 continues to change, and new variants may partially evade immunity formed after previous infections or vaccination. In 2026, the CDC continues to track new virus lineages through genomic surveillance, traveler data, and wastewater analysis.
Why wastewater is monitored
After the pandemic, many countries reduced mass testing, so the number of officially registered cases no longer gives a complete picture of COVID-19 spread. Wastewater has become one of the most useful monitoring tools.
People shed virus particles regardless of whether they have symptoms or not. Therefore, an increase in SARS-CoV-2 concentration in sewage samples can indicate rising spread of infection even before the number of doctor visits and hospitalizations increases. The CDC notes that increased viral activity in wastewater may signal a higher risk of infection in a specific region.
Who is still more at risk from COVID
For most young and healthy people, the risk of severe illness is now much lower than in the first years of the pandemic. However, COVID-19 can still lead to severe disease and death.
WHO primarily includes the following in high-risk groups:
- elderly people;
- people with weakened immune systems;
- patients with chronic diseases;
- people with multiple comorbidities.
It is precisely for these groups that increased local circulation of the virus has the greatest practical significance.
What can be done during summer rise in cases
If COVID-19 spread increases in a region, returning to all pandemic-era restrictions is usually not necessary. But a few simple measures can significantly reduce risk.
In crowded public transport, airports, and medical facilities, a well-filtering mask remains additional protection, especially for people in risk groups. It is also useful to ventilate rooms and, if possible, avoid close contact with elderly relatives or people with weakened immunity when experiencing symptoms of a respiratory infection. Before traveling or meeting vulnerable relatives, people with symptoms should consider taking a COVID-19 test.
And what about vaccination
Vaccination is now primarily aimed not at completely preventing infection, but at reducing the risk of severe disease, hospitalization, and death. Up-to-date vaccination is especially important for elderly people and patients in high-risk groups.
Specific recommendations for vaccination frequency vary between countries, so one should follow the national health system recommendations. For people living abroad or frequently traveling between countries, this is particularly important: revaccination schedules may differ in different states.
No new global wave yet
Despite local summer surges, the World Health Organization currently characterizes global SARS-CoV-2 activity as low. This is a fundamental difference from the first years of the pandemic.
However, the virus has not disappeared and continues to circulate year-round. Therefore, for most people, the summer rise in COVID means primarily a reason to consider the situation during travel and large gatherings, and for the elderly and other vulnerable groups— an additional reason to closely monitor the local epidemiological situation and doctors' recommendations.
Based on materials from: World Health Organization, WHO COVID-19 Global Risk Assessment, CDC
