Yes, you can get the flu in the spring. Influenza is a respiratory illness caused by a virus that circulates year-round, although its activity level changes dramatically. While the peak season is during the colder months, the virus does not disappear immediately once spring arrives. The flu is defined by the sudden onset of symptoms like fever, body aches, and fatigue caused by the influenza virus strains A or B.
Understanding Typical Influenza Season Timing
The period of high influenza activity, commonly called flu season, typically begins in the fall and extends through the winter, peaking between December and February. This predictable pattern is driven by environmental and social factors that favor the virus’s transmission. Influenza viruses survive longer when the air is cold and dry. Lower absolute humidity, common in winter, allows respiratory droplets containing the virus to remain suspended in the air for extended periods, increasing the chance of infection.
Behavioral changes also contribute to the winter peak, as colder temperatures force people to spend more time indoors and in close proximity. Increased indoor crowding in settings like schools and workplaces creates ideal conditions for the virus to spread rapidly. These drivers create the annual surge in flu cases characteristic of the winter months, which facilitates public health measures such as annual vaccination campaigns.
Why Flu Cases Persist into Spring
The flu season does not end abruptly; influenza activity gradually declines, often extending well into the spring months. Significant activity is commonly reported in March, April, and sometimes even into May. During the 40-year period between 1982 and 2024, flu activity peaked in March during six different seasons, demonstrating that late-season circulation is a regular occurrence.
Late-season spikes are attributed to the staggered waves of different circulating influenza strains. Influenza B strains often peak later than Influenza A strains, delaying the overall decline in cases. Furthermore, vaccine effectiveness can wane over several months, meaning individuals vaccinated early in the fall may have reduced protection later in the spring. This reduced immunity allows the virus to continue circulating and causing illness even as the weather warms.
Is It the Flu or Something Else?
When spring arrives, many people confuse lingering flu cases with other common seasonal illnesses, primarily colds and seasonal allergies. The flu is distinguished by its sudden onset and severe symptoms, typically including a high fever, extreme fatigue, and pronounced body aches. These severe systemic symptoms are rare with a common cold or seasonal allergies.
A common cold usually presents with milder symptoms that develop gradually, such as a runny nose, mild cough, and throat discomfort; a fever is uncommon. Seasonal allergies result from an immune system reaction to airborne substances like pollen, causing signs such as itchy eyes, an itchy nose, and watery discharge. Unlike the flu, allergies do not cause fever or the severe muscle aches associated with influenza.
The only way to definitively confirm an influenza infection is through diagnostic testing performed by a healthcare provider. If you suspect the flu, especially if symptoms begin suddenly with a high fever and severe body aches, seeking medical advice is important. Early diagnosis allows for consideration of antiviral medications, which are most effective when started within two days of symptom onset. Consulting a medical professional is advisable if symptoms are severe or if you belong to a population at high risk for flu-related complications.