Virus World

The cumulative hospitalization rate for flu in the U.S. is higher than it has been at this point for more than a decade. There are increasing signs that flu season is off to a very early start in parts of the United States, with the cumulative hospitalization rate higher than it has been at this point in the fall for more than a decade, the Centers for Disease Control and Prevention reported Friday.  In its weekly FluView report, the CDC estimated that there have already been 880,000 influenza illnesses, 6,900 flu hospitalizations, and 360 deaths caused by flu this season, which started at the beginning of October. It is unusual for the CDC to have enough data to issue estimates on the burden of flu this early in the season.  These figures are estimates, based on data from a flu hospitalization surveillance network of acute care hospitals in 14 states. Flu activity is currently highest in south-central and southeast parts of the country, and New York. It is also picking up along the Eastern Seaboard. The CDC also reported the death of a child, the first pediatric flu death of the new flu season. It occurred in the week ending Oct. 8. 

In the first two winters of the Covid-19 pandemic, the new coronavirus and the measures people took to protect themselves from it suppressed transmission of a number of respiratory pathogens that normally make the rounds. That hiatus has ended and those viruses are returning, though often at times when they didn’t normally circulate in the past. Hospitals around the country are seeing record numbers of cases of respiratory syncytial virus, or RSV, right now. In pre-Covid times, RSV didn’t typically emerge until the winter. Some people are interpreting the early start of flu activity as evidence we are in for a harsh flu season. But Lynnette Brammer, team lead for domestic surveillance in the CDC’s influenza division, said it’s impossible at this point to know how bad the season will be.  “What a lot of people are implying is because it’s early and levels are high for this time of year that it’s going to be a severe season. We don’t know that,” Brammer told STAT.  “Right now all we can say is we’re off to an early start.”  She noted that people who have been waiting to get a flu shot to try to time it to the start of flu circulation should not hold off any longer. “You need to get vaccinated now, if you haven’t already done that.” Ed Belongia, director of the Center for Clinical Epidemiology and Population Health at Wisconsin’s Marshfield Clinic Research Institute, said there is good reason to be worried that this could be a severe flu season. Most immune systems haven’t seen flu viruses for a couple of years, which means the pool of people susceptible to infection is large. And the measures society took to try to slow spread of Covid — mask-wearing, social distancing, school closures — have mostly been abandoned.  But Belongia has been studying flu for too long to guess how a flu season will unfold. The virus is maddeningly unpredictable. “Whether or not the whole season is going to be longer and more severe, we really just don’t know at this point. It’s too early to say,” he said.

Evidence from the Southern Hemisphere’s flu season — which sometimes provides hints of what’s in store for us — showed oddly timed and active flu seasons, but not necessarily bad ones. Australia had a lot of flu activity, mainly in children. But a report on its 2022 winter season issued earlier this month stated that the clinical severity of the season, based on the numbers of intensive care admissions and deaths, was actually low. It rated the overall impact of the flu season as low to moderate. Other hopeful news from the Southern Hemisphere was that the flu vaccine seems well-matched to the viruses that are circulating. A report this week from Chile in the CDC’s online journal Morbidity and Mortality Weekly Report estimated flu vaccine efficacy at 49% against H3N2 viruses, the subtype that caused most of the disease there. It is also the virus currently causing most disease in the U.S. Belongia said he was pleasantly surprised, adding  “49% is about as good as you can expect to see for H3N2. So I thought that was encouraging. While it’s impossible to guess how bad the flu season will be, there is one thing that does look reasonable to assume. If the current levels of circulation of influenza and RSV virus continue or increase, there could be a lot of respiratory illness around Thanksgiving. Much of the current illness is in young children, who typically get sick first in the cold and flu season and spread their bugs to siblings, parents, grandparents, and other adults with whom they are in contact.

The world is in uncharted waters for the 2020 respiratory virus season. For the first time in modern history, the Northern Hemisphere faces the prospect of the coronavirus disease 2019 (COVID-19) pandemic and a simultaneous epidemic of seasonal influenza. Each causes life-threatening illness and death, especially in older adults, people with chronic diseases, and other vulnerable populations. How can we prepare for this convergence?

The timing and severity of a COVID-19 wave in the fall and winter are uncertain, but past experiences with the 1918 and 1957 influenza pandemics point to the possibility of a resurgence. Almost nothing is known about the interaction of influenza virus and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, the cause of COVID-19) within individuals. Does coinfection increase the risk of severe illness or amplify virus shedding? Few coinfections have been reported from China during the early phase of the pandemic. The Southern Hemisphere influenza season is just beginning, and it may provide some clues as to what can be expected in the Northern Hemisphere later this year.

Much of the population remains susceptible to SARS-CoV-2, and the stress on hospitals will be greatest if the COVID-19 and influenza epidemics overlap and peak around the same time. It is possible that the number of individuals infected with each virus will peak at different times, reducing the peak demand for hospital beds. If a surge in COVID-19 cases occurs this fall, tightening mitigation strategies will be necessary. Social distancing and stay-at-home orders are socially and economically disruptive, but can reduce demand on hospitals and protect vulnerable populations. They will also reduce transmission of other respiratory viruses, including influenza and respiratory syncytial virus. Supplies of personal protective equipment must sufficiently meet the projected demand of a severe influenza season along with COVID-19....

Published in Science (June 12, 2020):

https://doi.org/10.1126/science.abd2220

Flu-related hospitalizations nationwide have risen dramatically in recent weeks, reaching levels historically not seen until much later in flu season, according to data released Friday by the Centers for Disease Control and Prevention. "We haven't seen this level of activity this early before," said Lynnette Brammer, team lead of the domestic influenza surveillance team at the CDC. Typical flu seasons usually don't pick up steam until December. Flu hospitalizations are rising across all age groups, especially children. The increase comes as other respiratory viruses, including RSV, or respiratory syncytial virus, are also spiking in kids. According to the Department of Health and Human Services, 76% of pediatric hospital beds nationwide are full. "We realize the potential implications of the co-circulating viruses all at once," Brammer said. "We're taking it very seriously."  Doctors are not required to report each positive flu test to public health officials, so the CDC and others monitor likely flu activity by looking at "influenza-like illnesses": a fever of at least 100 degrees Fahrenheit and a cough and/or sore throat without any other known cause.

Also Friday, the CDC reported the first flu-related death in a child so far this season. The CDC did not provide any details about the child, however KVEO, the NBC affiliate in Brownsville, Texas, recently reported that a 3-year-old girl had died after testing positive for the flu. While the flu and similar viral illnesses are rising nationwide, they're notably high across the Southeast and Eastern Seaboard — from Texas to Georgia, and South Carolina up to Virginia and New Jersey, according to the new report. Doctors also warn that other infections can follow severe cases of the flu, including bacterial infections like pneumococcal pneumonia. Dr. Greg Poland, director of the Mayo Clinic's Vaccine Research Group in Rochester, Minnesota, worries that this season could be bad for these post-viral infections.  Dr. Shannon Martinello, a pediatrician in private practice in New Haven, Connecticut, is already seeing an uptick in post-viral bacterial illness. "The more mucus they have, and the more congested they are, it increases their risk of ear infections," she said. "I always tell parents when their kids have flu, it's going to be a rough week, and they're going to get better," Martinello said. But if a child who has recovered from the flu starts to feel sick again a week or 10 days later, she advises parents to take the child back to the doctor. "I want to re-listen to his lungs and re-check his ears and make sure that something else hasn't happened as a secondary issue." 

There are early signs that this year's flu shot appears to work well at keeping people out of the hospital. A report on Chile's flu season, released Thursday by the CDC, found the vaccine was 49% protective against flu-related hospitalizations. That might seem low, but from 2015 to 2020, flu shot effectiveness in the U.S. ranged from 29% to 48%.  It's unclear whether this year's flu shots in the U.S. will be as effective as was found during Chile's flu season. But the shots used in both countries have one of the same targets: the H3N2 flu strain, which accounts for a majority of flu cases currently detected in the U.S. H3N2 is an influenza A virus and is often associated with increased hospitalizations. Kids under age 5 may be at particular risk. The CDC recommends that everyone 6 months and older get an annual flu shot. Children up through 8 years old may need two shots this year, the agency said, especially if they've never had the flu vaccine. The American Academy of Pediatrics has the same recommendation, adding that kids should get their flu shots by the end of October. But the early start to the flu season has left many Americans vulnerable. Only about half of the population gets an annual flu shot, typically. Many who do often wait until October to get it. "I cannot stress enough how important it is to go ahead and get that vaccine now," Brammer said.