July 14 (UPI) -- The rise of new COVID-19 variants and the growing number of people with "long-haul" symptoms of the coronavirus suggest it likely will remain a health challenge in the United States for years, experts said Wednesday.
This means that communities across the country will need to prepared to respond to outbreaks by reinstituting mask requirements and other measures, particularly in areas in which vaccination rates are low, they said.
"The number of new cases has more than doubled in the past two weeks alone and things could get much worse," epidemiologist Dr. David Dowdy said during a call with reporters hosted by the Johns Hopkins Bloomberg School of Public Health.
Infection rates in much of the country are at their lowest levels since April of last year. But many regions, particularly in the Midwest, are reporting COVID-19 outbreaks, largely fueled by the Delta variant that originated in India, according to the Centers for Disease Control and Prevention.
More than 20,000 new cases were reported Monday, more than double the daily figures seen in late June, and the variant accounts for more than half of them, the agency said.
At the same time, many parts of the country have relaxed restrictions on face coverings and large gatherings, Dowdy said.
"[If] case counts are going up, whether due to the Delta variant or not, we as a society are going to have to be prepared to institute some measures to control outbreaks," said Dowdy, an associate professor of epidemiology at Johns Hopkins in Baltimore.
More than 33.9 million confirmed COVID-19 cases have been reported in the United States, and nearly 608,000 people have died from the disease since the start of the pandemic in March 2020, Johns Hopkins estimates.
Infection rates began to decline this spring, as nearly 50% of adults in the United States were fully vaccinated against the virus, according to the CDC.
However, the recent uptick of cases in some areas of the country is concerning, given that vaccination rates are low in these areas and they have stalled in much of the country, Dowdy said.
The vast majority of cases of serious illness and deaths attributed to the virus in recent weeks are occurring in unvaccinated people, he said.
"There is no evidence that the [currently available COVID-19] vaccines are any less effective against the Delta or any other variants," he said.
The Delta variant is more contagious than earlier strains and may also strike younger people harder, according to the CDC.
It also is possible that children could bear the brunt of the effects of the variant, given that fewer of them are vaccinated, Dowdy said.
Less than 10 million of those ages 12 to 18 have received one dose of a COVID-19 vaccine, with 7 million in the age group fully vaccinated -- which equates less than 30% of teens and adolescents in the country, the CDC reported. COVID-19 vaccines are recommended for children age 12 and older.
It is likely that at least some of the children will become COVID-19 "long haulers," or those who have persistent symptoms ranging from severe fatigue and breathing problems to heart and kidney disease, Priya Duggal, a professor of epidemiology at Johns Hopkins, said on the call.
An estimated 10% to 30% of adults infected with the virus develop these persistent health complications, many for up to one year after they developed symptoms. Severe fatigue is common.
However, because much of the country's population is immune to the virus -- either through vaccination or previous infection -- it is unlikely that "we'll see the kinds of infection rates we saw last winter," Dowdy said.
"But it is also unlikely the virus will be eradicated in a few months, so we need to be prepared that this will be with us for years to come," he said.