How to Read CDC “Activity Levels” for COVID-19, Flu, and RSV (What to Do Next)

CDC’s “Respiratory Virus Activity Levels” use five labels—Very Low to Very High—to describe how respiratory viruses may be spreading in a community. These labels are not a personal risk score, and they don’t tell you which virus someone has.

Because no single data stream is perfect, CDC combines multiple signals—especially wastewater monitoring (an earlier community infection signal) and emergency department (ED) / acute respiratory illness (ARI) activity (a health-care seeking signal). CDC also considers severe outcomes separately to help readers understand potential impact.

Quick answer: what CDC “Activity Levels” mean

Think of the labels as a community “pressure gauge” based on surveillance. CDC uses the five levels to show whether respiratory illness activity in your area appears lower, rising, or higher compared with baseline periods.

Step-by-step: interpreting Very Low → Very High

In CDC’s system, the labels are based on how current ED/ARI activity compares to the baseline reference periods used in CDC’s definitions. In plain terms:

Very Low: at or near the baseline reference level.
Low: slightly above baseline.
Moderate: clearly above baseline.
High: much higher than baseline.
Very High: the highest category—well above baseline.

What to do with that information: use the label to adjust your family’s layered prevention habits and to be more deliberate about seeking care sooner if someone becomes sick—especially if they’re in a higher-risk group.

What wastewater tells you (and what it can’t)

Wastewater can be an earlier warning signal. CDC explains that wastewater monitoring can detect viral material in sewage before people necessarily seek care—sometimes capturing infections even when symptoms aren’t obvious.

Wastewater is not a complete picture. CDC also lists limitations that can affect how you interpret results, such as:

Coverage may be partial: wastewater monitoring may represent only a portion of the population served by that system.
Possible extra sources for flu: for influenza A, wastewater detections can reflect contributions from multiple sources, not only human illness.
RSV sampling challenges: CDC notes that some groups may be underrepresented in wastewater signals for RSV depending on how waste is handled (for example, where diaper waste is disposed outside the wastewater system).

Bottom line: wastewater helps you understand when community spread may be increasing or decreasing, but it’s best used alongside ED/ARI activity and other context—not as a single “risk answer.”

What ED/ARI activity tells you (and why it may differ from severity)

ED/ARI activity reflects health-care seeking patterns. CDC’s ARI metric is intentionally broad. It captures a range of acute respiratory illness visits, including visits for COVID-19, flu, RSV, and other respiratory causes.

That means ED/ARI activity can help you understand how much respiratory illness is showing up in care, but it does not automatically tell you:

whether most infections are very severe, or
whether severity among people infected is necessarily high.

CDC notes that estimates and trends can also be influenced by changes in how many people seek emergency care and by factors that may affect disease severity over time (like changes in viruses).

How CDC uses severe-illness context (and what it can’t tell you)

To help readers understand potential impact, CDC tracks severe outcomes separately (for example, serious respiratory illness requiring hospitalization and deaths). This can be especially important for families thinking about how strongly to protect higher-risk household members.

At the same time, surveillance is still surveillance: severe-outcome signals can lag and are influenced by reporting and other practical factors. So the activity labels are best viewed as together with severe-outcome context, and always alongside symptom-based judgment.

What readers can do next (home, school, and work)

At home: keep it practical—reduce spread when someone is sick

CDC guidance emphasizes staying home when you’re sick and taking extra precautions for the following days. A common approach in CDC guidance is:

Stay home until symptoms are improving and you’ve been fever-free for at least 24 hours (without fever-reducing medicine).
After that, take extra precautions for the next several days to reduce the chance of spreading to others.

For prevention, CDC recommends being up to date on recommended immunizations, improving indoor air when possible, and using basic respiratory hygiene (like covering coughs and staying home when you’re ill). Some people may also choose masking or testing during higher-activity periods.

Schools and child care: when to keep kids home

AAP HealthyChildren.org provides caregiver-friendly guidance for staying home when sick, including when a child:

has a fever (for example, above 101°F) in the past 24 hours,
has had vomiting or diarrhea in the past 24 hours, or
isn’t well enough to participate comfortably in class.

Families should also follow their school or district attendance policies, since requirements can vary.

At work: plan “layered, not panicked” safety

If your local activity label is moderate through very high, consider practical steps such as:

encouraging sick employees to stay home,
improving ventilation in shared indoor spaces, and
being thoughtful about how people who are higher risk are protected during close indoor contact.

Who should pay extra attention?

CDC notes that some people are more likely to become severely ill from respiratory viruses. Higher-risk groups can include:

Adults 65+
Children younger than 2 years
People with underlying medical conditions (like chronic lung disease, heart disease, diabetes, or chronic kidney disease)
People with weakened immune systems, disabilities, or who are pregnant

If you care for someone higher risk, use activity levels as a cue to be prepared—have prevention supplies on hand and know how you’ll seek care promptly if symptoms start.

When to seek care or emergency help

Activity levels can help you plan, but they don’t replace symptom-based decisions. If you or your child have emergency warning signs, seek emergency care immediately.

Adults: emergency warning signs can include difficulty breathing/shortness of breath, persistent chest or abdominal pain/pressure, confusion, inability to arouse, seizures, not urinating, severe weakness, or fever and cough that improves then returns or worsens.

Children: emergency warning signs can include fast breathing or trouble breathing, bluish lips or face, ribs pulling in with each breath, chest pain, dehydration (for example, no urine for about 8 hours or no tears when crying), lack of alertness, seizures, or in young children, any fever at or above 100.4°F in children younger than 12 weeks.

The bottom line

CDC’s five “Activity Levels” are a practical way to translate community surveillance into a simple message. Use the label to support calmer, layered choices—especially to protect higher-risk people—and rely on CDC’s severe-outcome context and symptom-based judgment to decide what care is needed.

Sources

Editorial note: Weence articles are researched from cited public-health, medical, regulatory, journal, and reputable news sources and may be drafted with AI assistance. They are checked for source support, clarity, and safety guardrails before publication.

This article is for general informational purposes only and is not medical advice. Research findings can be early or incomplete, and health guidance can change. Always talk with a qualified healthcare professional about personal symptoms, diagnosis, medications, vaccines, screenings, or treatment decisions. If you think you may have a medical emergency, call emergency services right away.