A “tripledemia”? Flu and other infections are returning as COVID-19 cases rise.

A walk-in COVID testing site at the Esperanza Heath Center in Chicago on Sept. 13, 2022. (Jamie Kelter Davis/The New York Times)

For more than two years, schools and offices closed, social distancing and masks have given Americans a reprieve from the flu and most other respiratory infections. This winter is going to be different.

With little to no restrictions in place and travel and socializing in full swing, an expected winter spike in COVID-19 cases looks set to collide with a resurgent flu season, sparking a so-called twindemic – or even a tripledemic, with a third virus, respiratory syncytial virus, or RSV, in the mix.

Flu cases have started showing up earlier than usual and are expected to spike over the next few weeks. Children infected with RSV (which has symptoms similar to the flu and COVID-19), rhinoviruses and enteroviruses are already straining children’s hospitals in several states.

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“We see it all coming back with a vengeance,” said Dr. Alpana Waghmare, an infectious disease expert at Fred Hutchinson Cancer Center and physician at Seattle Children’s Hospital.

Most cases of COVID-19, influenza and RSV are likely mild, but together they can sicken millions of Americans and swamp hospitals, public health experts have warned.

“You have this waning COVID immunity, which coincides with the impact of the flu coming here, and RSV,” said Andrew Read, an evolutionary microbiologist at Penn State University. “We are in uncharted territory here.”

Vaccines against COVID-19 and the flu, even if they don’t prevent infection, still offer the best protection against serious illness and death, experts have said. They urged everyone, and especially those at high risk, to get vaccinated as soon as possible.

The elderly, immunocompromised people and pregnant women are most at risk, and young children are highly susceptible to influenza and RSV. Many infected children become seriously ill because they have little immunity, either because it has waned or because they were not exposed to these viruses before the pandemic.

RSV causes approximately 14,000 deaths in adults 65 and older and up to 300 deaths in children under 5 each year. No vaccine is available, but at least two candidates are in late-stage clinical trials and appear to be very effective in older people. Pfizer is also developing an antiviral drug.

“To date, we are seeing an equal number of COVID, influenza and RSV, and this is really concerning because we are very early for influenza and RSV activity,” said Dr Diego Hijano, specialist. pediatric infectious diseases at St. Jude Children’s Research. Hospital.

“The winter is going to be tough,” he said.

Another wave of COVID-19?

Coronavirus cases are low but are starting to rise in some parts of the country. Several European countries, including France, Germany and Britain, are seeing an increase in hospitalizations and deaths, prompting experts to fear that the United States could follow suit, as in previous waves.

Some of the growing coronavirus variants are adept at dodging immunity and drugs such as Evusheld and Bebtelovimab, which are particularly important in protecting immunocompromised people.

People with compromised immune systems “remain at risk even despite getting all recommended or even additional vaccine doses,” Waghmare said.

Public health experts are particularly concerned about a constellation of omicron variants that appear to evade immunity against vaccines and even recent infection better than previous variants.

The latest booster vaccines made by Pfizer and Moderna were designed for the variants that dominated last summer, but not for these newer variants. Still, they boost antibody levels overall and should help stave off severe symptoms and shorten the duration of illness, said Aubree Gordon, a public health researcher at the University of Michigan.

The BA.5 variant was the most immuno-evasive variant until recently, but is rapidly being replaced by others, including two that show an even greater ability to evade immunity.

One of them, known as BQ.1.1, is the prime candidate for causing a winter surge, and it has already skyrocketed cases in Europe. Although it and a closely related variant called BQ.1 together account for only about 11% of cases in the United States, their share rose rapidly from just 3% two weeks ago.

A combination of two omicron subvariants called XBB has fueled a surge of cases in Singapore, among the most vaccinated countries in the world. Its XBB.1 subvariant has just arrived in the United States. Another variant, called BA.2.75.2, is also highly immune evasive and causes more severe disease, but is so far responsible for less than 2% of cases nationwide.

Most other variants do not appear to cause more severe symptoms than earlier versions of the virus, but the trend of immune evasion is expected to continue, experts said.

“Now things have changed with the massive degree of immunity people have against previous variants,” said Cornelius Roemer, a computational biologist in Richard Neher’s group at the University of Basel.

The Food and Drug Administration has licensed boosters designed for BA.5 for all Americans ages 5 and older, but so far only a small fraction of those eligible for a vaccine have received one. Less than a third of children aged 5 to 11 have even completed the first round of COVID-19 vaccines.

That could change as people see a rapid rise in cases, Gordon said.

Sign of a bad flu season

Before the coronavirus hit the world, flu viruses sickened millions of people every winter and killed tens of thousands of Americans. During the 2018-19 season, the flu was responsible for 13 million medical visits, 380,000 hospitalizations and 28,000 deaths.

The flu season in the southern hemisphere, usually between May and October, is highly predictive of winters in the northern hemisphere. This year, the flu started weeks earlier than usual in Australia and New Zealand, and the number of cases and hospitalizations were significantly higher.

Gordon tracks flu rates among children in Nicaragua, which has a flu season spanning June through July, and a heaviest one in late fall. More than 90% of the population was considered fully vaccinated against COVID-19 last January, and many people had also acquired immunity against one or more infections.

Still, the country has seen high rates of COVID-19 and influenza in the first half of this year. Childhood flu rates were higher than during the 2009 flu pandemic, and children were on average sicker than in previous years. “We’ve seen a lot of hospitalizations,” Gordon said.

In the United States, the flu usually begins to show up in October and continues through March, peaking between December and February. But in some states, the season is already underway.

About 3% of tests nationwide were positive for the flu as of Oct. 8, according to the Centers for Disease Control and Prevention, but rates are above 10% in some southeastern states and above 5% in the south-central region. . In Texas, the proportion of positive flu tests jumped to 5.3% in early October from 3.7% the previous week.

Some southern states are also reporting an increase in ventilator use. In New York, health officials said this month that the flu was already widespread in the state.

Public health experts have urged Americans, especially those at high risk, to get their flu shot before cases rise much more. Like COVID-19 vaccines, the flu shot may not be a perfect match for the circulating variant, but even so, it roughly halves the risk of hospitalization in children and adults.

Antibodies kick in about two weeks after an injection, so a vaccine can now actually extend protection during the winter surge better than a vaccine received in September.

Last year, flu vaccination rates declined slightly in all age groups compared to the previous year, according to a CDC analysis. The vaccination rate for children aged 6 months to 4 years, who are at high risk, showed the biggest drop – to 67% from 75% before the arrival of the coronavirus.

The lower rate may be because distrust of COVID-19 vaccines has spread to those against the flu, or simply because parents have forgotten about the danger the flu poses to young children. It is too early to tell if the numbers will improve this year.

Older people and people with compromised immune systems should get both COVID-19 and flu shots, public health experts have said. Healthy young adults may also want to opt for both vaccines if they don’t want to get sick or can’t afford to miss work, or to protect others around them who are at higher risk.

Some communities are at increased risk of severe illness and hospitalization for influenza. During the 2009-22 flu seasons, hospitalization rates were 80% higher among black adults, 30% higher among Native American/Alaska Native adults, and 20% higher among Hispanic adults compared to white adults, according to a CDC report released last week.

Yet flu vaccination rates were much lower in these groups. Immunization coverage also fell about 9 percentage points from the previous year among pregnant women of all racial and ethnic groups.

In February 2020, Gordon was preparing to talk to his 7-year-old daughter’s class about coronavirus when a boy in the class died of an influenza B virus infection.

“Most of the time it doesn’t make you very sick, but sometimes it can,” Gordon said of the flu. “We have an effective flu vaccine, so I encourage people to go get the shot.”

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