What's Going Around in Ontario?
Health data for the Ontario, California area — April 2026
Here's what respiratory illnesses and infectious diseases look like near Ontario, California, based on the latest CDC surveillance data for California. Tap any topic for detailed state-level trends, charts, and forecasts.
3.7% ILI
↓ Declining in California
1.0 per 100K
↓ Declining in California
0.5 per 100K
↘ Likely Declining in California
20 cases in California
96.1% in California
CDC Recommendations at This Level
Active measles outbreak — vaccination is urgent
- • The CDC strongly recommends MMR vaccination for anyone who is not up to date
- • Measles is extremely contagious — it spreads through the air and can linger in a room for 2 hours after an infected person leaves
- • If you develop symptoms, call your doctor BEFORE going in — they need to prepare to avoid exposing others
- • Unvaccinated individuals should avoid public spaces where cases have been reported
- • Infants too young for MMR (under 12 months) should avoid known outbreak areas
This is general public health guidance based on CDC recommendations — not personal medical advice. Talk to your healthcare provider about what's right for you and your family.
Ontario Community Health Snapshot
2022 dataCity-specific chronic disease and prevention statistics from the CDC PLACES program , which provides local health estimates for communities across the US.
Chronic Conditions
Mental Health
Health Behaviors
Prevention & Access
Source: CDC PLACES: Local Data for Better Health, 2024 release. Age-adjusted prevalence estimates. Learn more
About this data: Infectious disease surveillance (flu, COVID, RSV, measles) is reported at the state level. This page uses California data as the best available indicator for the Ontario area. The health snapshot above shows Ontario-specific estimates from CDC PLACES (2022 data).
See the full California health dashboard for more detail.
Frequently Asked Questions
What illnesses are going around in Ontario, California right now?
Based on California state surveillance data (which covers Ontario), flu activity is moderate, RSV is low, COVID-19 is low, and California has reported 20 measles cases in 2026. Click any topic above for detailed trends and charts.
Is the flu bad in Ontario right now?
Flu activity in California (which includes Ontario) is currently moderate with 3.7% ILI. The trend is declining, which is good news. See the California flu page for weekly trend charts.
What are the biggest health issues in Ontario?
According to the CDC PLACES dataset (2022 data), Ontario residents face these key health challenges: Sleep Deprived (38.2%), Obesity (33.5%), High Cholesterol (32%). The community health snapshot on this page shows 18 health measures specific to Ontario.
Does Ontario have its own health data, or is this state-level?
This page combines two types of CDC data. The infectious disease section (flu, COVID, RSV, measles) shows California state-level surveillance, which is the most reliable available indicator for the Ontario area. The Community Health Snapshot below shows Ontario-specific chronic disease and prevention data from the CDC PLACES program, which provides city-level estimates for all 50 states. State infectious disease data reflects overall trends that apply to communities within the state, including Ontario.
Local Health Signal is not affiliated with the CDC or any government agency. Data is provided for informational purposes only and is not intended for clinical decision making. See our methods page for details on data sources and limitations.