COVID-19 cases in the US appear to be on a downward trend, according to a report from the US Centers for Disease Control and Prevention and the New York Times COVID-19 tracker. But most counties in the US still have a "medium" or "high" level of COVID-19, which continues to guide COVID-19 recommendations after the CDC recently updated its guidance. The updated guidance removes the quarantine recommendation for people who aren't vaccinated and other adjustments as the CDC tries to move the US into a new phase of COVID-19.  

The cause of most COVID-19 infections this summer is BA.5, the newest subvariant of the omicron variant. Scientists believe BA.5 is the most contagious version of COVID-19 thus far, and it's responsible for about 89% of current cases, according to the latest data from the CDC. 

At a White House COVID-19 Response Team briefing July 12, Dr. Anthony Fauci, the president's chief medical adviser, explained how the virus that causes COVID keeps mutating and that the virus has "essentially bumped one variant off the table after the other," which has led to a long parade of increasingly contagious subvariants of omicron. BA.5 is the newest, and a highly problematic, mutation.

Though BA.5 "substantially" evades antibodies from prior infections and vaccines, health officials say being up-to-date with a booster (or two boosters if you're 50 or older) still protects against severe disease and death. Research so far shows that BA.5 doesn't overcome those protections against severe disease, though more research is needed to understand its clinical severity compared with earlier subvariants of omicron.

In an effort to target the most relevant strain of virus causing COVID-19, vaccines based on the BA.5 subvariant (along with BA.4) will be the first choice for COVID-19 booster shots this fall, to be rolled out as early as September. Response Team Coordinator Dr. Ashish Jha encouraged everyone to get a booster if they're eligible and haven't opted for one yet, because it won't affect people's ability to get vaccinated come fall or winter when they become eligible. Second boosters of the existing vaccines will likely only be recommended until then for adults 50 and up and younger adults and teens who are immunocompromised.

COVID-19 treatments, including Paxlovid, are predicted to be effective still, and the US Test to Treat clinics are still up and running to connect people most at risk with prescriptions for treatments if they need them. 

Here's what we know about BA.5. 

Read more: Best COVID Face Masks For Kids  

Do the at-home tests detect BA.5?

Right now there's no reason to suggest that the at-home rapid COVID-19 tests (a few boxes of which are free when you order through the government's website) are less effective in regard to BA.5 compared with earlier versions of omicron. Generally speaking, the FDA says early data suggests the antigen tests detect omicron but may have reduced sensitivity. BA.5 is a version of omicron, and tests are expected to work the same. 

But as of last week, the FDA strengthened its stance on the importance of testing more than once. To be positive you don't have COVID-19, the FDA says you should take a third test if the first two were negative, but you're concerned you were exposed to COVID-19. Taking another home test 48 hours after your second negative test will help catch an infection, as a study found that repeat testing over a longer time frame is more accurate, per the FDA.

"Positive results remain highly accurate for these tests, though there still can be false negatives," Shaili Gandhi, vice president of pharmacy at SingleCare, said in an email. This is because it takes a higher amount of virus to test positive on a rapid test than the highly sensitive PCR or lab-based tests. People who are fully vaccinated and boosted, for example, may have a very low viral load (smaller amount of virus) and that may mean they test negative even if they do have COVID-19.

Typically, rapid home tests work by detecting the part of the COVID-19 virus protein that doesn't change much between variants, called the nucleocapsid, Slate reports. "Because of that, the tests are able to detect the different variants," Nate Hafer, an assistant professor of molecular medicine at UMass Chan Medical School, told the publication.

Long story short: take the test.

Read more: New Booster for COVID: Here's the Fall 2022 Vaccine Plan

How severe is BA.5? Do COVID-19 treatments still work? 

BA.5 is a subvariant of omicron, which means it's different from the "original" omicron, but not different enough to constitute its own variant status. (Delta is a different variant from omicron and beta, for example.) BA.5 is understood to be the most contagious version of the virus yet, however, and it's evading immunity. This means more people will get reinfected with COVID-19, which can put them at risk of complications and long COVID symptoms, even if the infection itself was mild. 

Walensky said last week that we don't definitively know yet about the clinical severity of BA.5 compared to earlier subvariants of omicron. As the pandemic drags on and most of the population has some immunity from vaccines and prior infections, it can become harder to compare variant and subvariant severity in the real world. 

In an analysis of a preliminary (not yet peer-reviewed) report from the Kirby Institute in Australia, however, Dr. Eric Topol, a professor of molecular medicine at Scripps Research, wrote that BA.5's ability to infect cells might be more similar to the delta variant than other versions of omicron. He also writes that changes in BA.5 might explain reports of people taking longer to test negative compared to illnesses with earlier omicron subvariants. 

As with other versions of omicron that whittled down our immunity, the vaccines and boosters available are still expected to provide protection against severe disease and death. Boosters -- including a second booster -- have been particularly important for protecting older adults and other people more vulnerable to severe disease in the age of omicron, and have substantially cut the risk of death from COVID-19.

Paxlovid, an effective antiviral medication, is still expected to be effective at treating COVID-19 in people at higher risk of severe disease, Fauci said. The monoclonal antibody therapy available, bebtelovimab from Eli Lilly, is also predicted to be effective against BA.5, as is Evusheld. Evusheld  

If you test positive for COVID-19 and are at higher risk of severe disease (you're an older adult or you have a health condition), reach out to your doctor or find a Test to Treat clinic near you. 

What are the symptoms?

Right now, there aren't any reports that show BA.5 is giving people different symptoms compared to earlier versions of omicron. 

For many people who become sick with COVID-19 these days (particularly those who are fully vaccinated and boosted), symptoms resemble cold symptoms such as sore throat, runny nose and fatigue. Back pain is a peculiar new symptom of COVID-19 that some people with omicron have reported, and the once very common loss of taste or smell appears to be much less common with omicron variants than with older strains.

If you have symptoms and are wondering whether it's COVID-19, taking a test and staying home while you're sick will help protect people more vulnerable to severe COVID-19 disease. 

Read more:  Is It Allergies or COVID? How to Tell the Difference  

Understanding omicron, variants and subvariants 

Variants are made up of multiple lineages and sublineages. Each variant has a "parent" lineage, according to the CDC, followed by other lineages, which you can think of like a family tree. As the virus spreads between people, mutations occur, but not all of them change the characteristics of the virus in meaningful ways. 

The omicron variant and its sublineages made the virus much more contagious and capable of infecting more people, but it's led to less severe disease, on average, than the delta variant. 

One of the most important things we can do to stop the virus from mutating is keeping community levels of COVID-19 low so the virus has less chance to mutate, Fauci said. 

Genomic surveillance can detect variants and sublineages. Scientists in South Africa were able to quickly identify omicron as a new variant because of the way it presents through PCR tests. The original omicron causes a dropped signal or marker on the test that sets it apart from delta, which was the dominant variant prior to omicron. BA.2, however, didn't have the same signal, called an S gene target failure. This made it more "stealthy" and gave it its name. Genomic sequencing will detect all omicron subvariants and coronavirus variants in general.

However, detecting new variants or subvariants may be becoming more difficult as the number of sequences shared across the world have "dropped precipitously," Dr. Maria Van Kerkhove, an infectious disease specialist with the World Health Organization, said in June. While the impact was still enormous, having real-world data available quickly after scientists detected omicron was a benefit during the worldwide surge last winter. 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.