Delta variant: Things you should know | Coronavirus | UC Davis Health

Delta variant: Things you should know about this COVID-19 strain

Updated Jan. 27, 2023

The delta variant, which originated in India, began spreading rapidly and making news around the middle of June 2021. Here's what health experts have learned about the delta variant:

Delta variant symptoms are the same

The symptoms of the delta variant appear to be the same as the original version of COVID-19. However, physicians are seeing people getting sicker quicker, especially for younger people. Recent research found that the delta variant grows more rapidly – and to much greater levels – in the respiratory tract.

Typically, vaccinated people are either asymptomatic or have very mild symptoms if they contract the delta variant. Their symptoms are more like those of a common cold, such as cough, fever or headache, with the addition of significant loss of smell.

Learn how to schedule your COVID-19 vaccine at UC Davis Health

Learn the symptoms of COVID-19 and what symptoms will likely show first

Many unvaccinated patients with COVID-19 wish they had gotten the vaccine

UC Davis Health physicians have noted that a number of younger patients, when they come in with critical illness, say that they wish they would have gotten the COVID-19 vaccine. Many patients have told their physicians, "Why did I not get the vaccine?" or "Why did I not listen?"

Read from UC Davis Health: Patient shuns COVID-19 vaccine, then changes his mind after hospitalization

Wear masks to protect against delta and other variants, even if you're fully vaccinated

Health experts across the country are wearing masks themselves even though they're fully vaccinated to protect against the delta variant and other COVID-19 mutations. They're also advising vaccinated people to avoid large gatherings and mask up indoors where the vaccination status of other people is unknown.

UC Davis Health experts answer your questions about masking

Learn how to schedule your COVID-19 vaccine at UC Davis Health

Omicron BA.5 variant has taken over

In the late summer and fall of 2021, the delta variant was the dominate strain of COVID-19 in the U.S. Since summer 2021, the omicron BA.5 variant took over as the main mutation of COVID-19 in the fall of 2022. Although the omicron BA.5 variant is likely more contagious than any other strain to date, it generally causes less severe symptoms than the delta variant.

Get the latest on the omicron BA.5 variant and symptoms