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Respiratory viruses down in WA, but still circulating at high levels

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Credit: Unsplash/CC0 Public Domain

Holiday season has passed. Gatherings have slowed. But don't let your guard down just yet—experts say we're still in the midst of respiratory virus season.

COVID-19, influenza and RSV—known to many working in infectious disease as the "Big Three" viruses—continue to sweep through Washington state and the U.S., keeping community transmission levels high and straining some as a new COVID variant takes hold.

There's some good news: The fall rise of COVID hospitalizations has slowed and have declined in recent weeks, according to the most recent reports from the Centers for Disease Control and Prevention. The state's RSV hospitalizations have dropped significantly since late December.

"That's hopefully a good sign," said Pavitra Roychoudhury, a research assistant professor of laboratory medicine and pathology at the University of Washington. "But others have cautioned that sometimes you see a little bit of a dip before Thanksgiving, Christmas and New Year's, then another bump, then a slight dip again. Then, kids go back to school and things sometimes pick back up."

In Washington, COVID hospitalizations started to rise in September and early October, before taking a dip in November, the CDC reported. Hospitalizations ticked back up around mid-December, accounting for about 3.4% of total hospitalizations, according to the state Department of Health's respiratory virus data dashboard. As of Jan. 13, the figure had dropped to about 2.6% of total hospitalizations.

Respiratory virus-related emergency visits, hospital admissions and ICU beds occupied are all down from the prior week, the dashboard reports.

The numbers are nowhere near where they were during the surge of the omicron variant two years ago—when COVID patients made up more than 15% of emergency visits and nearly 20% of all hospitalizations. They're also lower than they were at this time last year, which recorded a rapid early start to RSV and flu season.

But the amount of respiratory virus circulating throughout Washington is still at "elevated" levels, said Dr. Scott Lindquist, the state's health officer. More than 400 people have died from COVID so far this season.

"When we were in the real thick of COVID, everyone was being real careful about hand-washing, mask-wearing, not going to school or work when sick," Lindquist said. "We essentially saw an absence of RSV and flu then. So these are lessons to be learned. We need to continue to apply them."

Last fall, more than a dozen local health departments and hospital systems around the region came up with a plan to determine when to bring back indoor masking requirements in health care facilities, where there are generally more people at risk of severe infection or death if they catch a respiratory virus.

According to the agreement, participating systems would reactivate masking policies if RSV, flu or COVID levels reached the "transmission alert threshold" (different for each virus) for emergency visits, which capture more timely data when people are developing symptoms—versus hospitalization numbers, which have more of a delay. Facilities will also bring back indoor masking if the CDC's COVID hit "medium" levels, meaning a hospital admits more than 10 new COVID patients per 100,000 people within a given week.

For influenza, the alert threshold for ER visits is 1% of total visits; for RSV, the threshold is 0.3% of total ER visits; and for COVID, the threshold is 3% of total ER visits.

The approach aims to balance community disease transmission rates and the "operational needs" of facilities to support staff and patient safety, according to the Northwest Healthcare Response Network, a coalition of Washington health care systems. The policies are not a legal requirement, and not all hospitals in the state have joined.

"They indicate a level of once you get to a certain number of ER visits for a specific respiratory virus illness, you're almost always going to see a peak," said Snohomish County health officer Dr. James Lewis. "If you remain below, you're likely going to either stay low or go down."

Once emergency visits for all three viruses are below their respective transmission alert thresholds and CDC COVID hospital admission levels are below "medium" for two weeks, health care facilities can then relax universal masking policies, per the agreement.

In Washington, although flu and RSV hospitalizations are down, both viruses are still above their transmission alert thresholds, now accounting for 2% and 1% of ER visits, respectively. COVID patients make up about 2% of ER visits—just below its alert threshold.

"This is indicating that there remains a lot of community transmission of these infections," said Dr. Eric Chow, chief of communicable disease, epidemiology and immunization for Public Health—Seattle & King County.

Several hospitals in the Puget Sound region have already brought back indoor masking for staffers, patients and visitors.

"This is the time where we should be thinking, 'Okay, if I get on an airplane, I should probably wear a mask,'" Lindquist said. "If I go to a crowded event, like a ballgame, I should consider wearing a mask."

He acknowledged the resistance many Washingtonians might feel around returning to widespread masking mandates, which is why that's not something state officials are currently considering.

"(This metric) certainly provides the data, certainly honors hospitals and health care settings, certainly thinks of protecting those that are most vulnerable, but again, leaves some ability for local control," Lindquist said.

Past the peak?

While second waves of flu and RSV are generally not common during a respiratory virus season, another surge is not impossible, Lindquist said.

Consistent declines in recent hospitalizations and ER visits give him "guarded optimism" that the state has hit its peak for flu and RSV, but clinics are still seeing a lot of patients with respiratory viruses, Lindquist said.

"Right after the holiday season, it is very common for us to see fluctuations in trends of these infections, in part because there's a change in health care-seeking behavior," Chow said. "Clinics are not always open, and people are not necessarily testing at that time."

Potential future COVID waves are still hard to predict, particularly with the emergence of new variant JN.1, which in December became the most widely circulating COVID variant in the U.S. and currently makes up about 86% of infections nationally. In Washington, state data shows JN.1 accounts for less than 3% of infections, though Chow noted that because not very many people are testing themselves for COVID, and therefore are contributing to a smaller sample size, there might not be the "same degree of accuracy" to predict how many infections in King County, for example, are attributable to any one variant.

Public health experts also pointed to the state's wastewater concentration levels, which captures the amount of pathogens circulating within a given community, as a useful indicator for what could be ahead.

Nationally, the CDC reported COVID activity in wastewater remains "very high"—the highest levels since the omicron wave—though local health experts pointed out a few caveats.

Wastewater data doesn't directly translate to case numbers. It only captures samples from specific sewage systems and it can be influenced by levels of precipitation that could change the concentration of viral particles, Chow said. Individual people shed different concentrations of virus, which can also vary by COVID variant.

In Washington, Lindquist reported that although there are some hot spot wastewater sites, many are "below activity."

West Point Treatment Plant, which covers parts of King and Snohomish counties, is one such hot spot, recording a significant jump in SARS-CoV-2 concentrations since late August.

"Given that prior peaks for flu have been as late as February, it's good to keep watching for a few more weeks," Roychoudhury said.

Advice for Washingtonians

Roychoudhury knows she sounds like a broken record when it comes to protecting against severe flu, RSV and COVID infections.

But the advice remains the same: Get vaccinated against COVID and influenza (and RSV, if you're eligible). Wear a mask in crowded, indoor settings—especially if you're at risk of severe infection or death, or if you're often around someone who is. Don't go to work or school if you're sick. Ask your doctor about taking antivirals if you get sick with the flu or COVID.

Despite the state's high levels of vaccination during the height of the pandemic, vaccine uptake has dropped significantly with the recent rollout of new shots. About 69.3% of Washingtonians have completed their primary series, but just 16.8% are considered up-to-date, meaning most people have not received a new 2023 shot, which became available last fall.

Public health experts continue to debate whether multiple COVID infections will make a person more susceptible to developing long COVID, but Chow pointed to one 2022 study out of the VA Hospital that suggests risk of long COVID does seem to increase as people become reinfected.

"What we do know about long COVID is that whatever we can do to reduce our risk of infection and more severe disease at the acute phase will also likely reduce our risks of longer term symptoms," Chow said. "That's where vaccination plays an important role. Testing and getting treated early is also really critical."

If you do think you have COVID, flu or RSV, health officials recommended getting tested in a medical setting, which would help dictate treatment options, but encouraged against showing up at the ER unless symptoms become life-threatening.

Urgent care centers can also provide testing.

"At this point in the year, I know people are eager to see downward trends and try to interpret that, but the reality is that even if things were to be truly down trending right now, levels remain relatively high," Chow said. "If people start to change their behaviors, it's actually very likely they're going to still get an infection. We're in the thick of things."

2024 The Seattle Times. Distributed by Tribune Content Agency, LLC.

Citation: Respiratory viruses down in WA, but still circulating at high levels (2024, January 22) retrieved 24 May 2024 from https://medicalxpress.com/news/2024-01-respiratory-viruses-wa-circulating-high.html
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