The world has avoided a ‘twindemic,’ but as flu cases rise alongside covid, experts fear that could change

A “twindemic” of covid-19 and influenza is a recipe for public health nightmares.

Strict measures to control the spread of the coronavirus were expected to prevent flu transmission, which appears to have largely held true for 2020. Some countries will be hardest hit this flu season while others may be spared.

Efforts to track flu cases face obstacles, as flu tests are not ubiquitous and the illness can be confused with others, including covid-19. Many health-care organizations track flu-like symptoms in hospitalizations.

The potential winter surge of coronavirus infections could coincide with another major public health event: the seasonal flu. This is what you should know. (Drea Cornejo, Daron Taylor/The Washington Post)

The United States, experts warn, could soon be facing its first “twindemic” season. Flu cases in America fell to record levels last winter as coronavirus soared. Flu cases in the United States are on the rise, along with the extremely contagious Omicron variant which has already overrun hospitals. Europe’s flu season has just begun and is expected to get worse.

Other places, including Israel, are seeing flu spikes this winter after historically low case levels last year. The trend is different for Australia which saw low flu cases last winter and has seen fewer in the summer when flu season hits.

And some countries, such as Brazil, are battling out of season flu outbreaks as they brace for the full effects of the fast-spreading omicron variant.

Israel recorded no influenza cases during its 2020 flu season. Hospitals are already at capacity for flu cases, while coronavirus infections are on the rise.

As of early December, Israel had recorded around 280 flu hospitalizations since September, when the season began, about double those seen during that same period in 2019, the last ordinary flu season before the coronavirus pandemic. By mid-December, 565 people had been hospitalized with the illness, according to the Israeli Center for Disease Control. Of those, 239 were in pediatric wards and 39 in maternity wards.

Steve Walz, the spokesman for Sheba hospital, which is Israel’s largest, said in late December that the hospital was “operating at almost 100 percent capacity” due to flu cases, while, at that time, he could count “on one hand” the number of people hospitalized for covid-19.

Compared to last winter, mask use and social distancing are far less widespread in Israel, which could partly account for the flu’s resurgence. Though the country in late November banned international travel because of the omicron variant, in general in recent months its borders have been more open than in the lead-up to winter 2020.

Australia kept its borders shut to travelers for much of the past two years. This has likely also helped to keep flu at bay.

Australia’s flu season typically ranges from May to August, the Southern Hemisphere’s winter months. In 2019, the country recorded some 950 flu deaths and 313,033 infections, surpassing the five-year average, the Australian Broadcasting Corporation reported.

Infections nosedived in 2020, when Australia recorded around 20,000 flu cases and 37 deaths.

But then flu infections dropped even further in 2021, with Australia recording less than 500 cases and no related deaths that season. Australia’s Department of Health logged just one hospitalization.

The decline in cases was recorded despite a slight drop in flu vaccination rates in 2021, with 74 percent of the population receiving the shot in 2021, 82 percent in 2020 and 77 percent in 2019, according to the Ministry of Health’s flu tracker.

One explanation could beAustralia’s coronavirus-related restrictions on travel to and within the country, which “likely disrupted external and local seeding” of the flu virus, World Health Organization spokeswoman Margaret Harris said in an email.

Ian Barr, the deputy director for the WHO Collaborating Center for Reference and Research on Influenza based in Melbourne, told the ABC that the majority of this summer’s flu cases were recorded in quarantine centers set up for incoming international travelers.

“The whole influenza world is topsy-turvy at the moment,” he said.

In December, officials in Rio de Janeiro started setting up mobile clinics to deal with influenza patients flooding emergency departments and doctors’ offices. By mid-December, the city recorded more than 21,000 infections — a more than 2,600 percent increase over just three weeks, according to the Brazilian Report.

Demand for flu vaccines also rose, and the city couldn’t keep up: It temporarily suspended its vaccination program as it waited for the Butantan Institute in Sao Paulo to send an emergency 400,000 million doses, Brazil’s state media reported.

Days later, Sao Paulo reported that a similar flu strain was behind its rising rate of emergency room visits and hospital admissions. Nancy Bellei, the coordinator of testing at a Sao Paulo hospital, told Brazilian media in mid-December that the rate of flu hospitalizations over the past week had been higher than during the flu’s typically peak period from March to June.

Out-of-season outbreaks are not uncommon in Brazil, especially this year, Harris said.

“Due to low levels of flu virus circulation for the last two years [around the world], it will not be surprising if influenza activity resurges during or out of season, as countries adjust their public health measures in response to the covid-19 pandemic,” she said.

Last year, flu cases dropped across the Southern Hemisphere. Public health officials are particularly concerned about this year’s flu epidemic, which comes along with an increase in coronavirus infections.

Since March 2020, about 616,000 people have died of covid-19 in Brazil, a death toll second only to that of the United States. However, Brazilian President Jair Bolsonaro opposed any measures that would limit spread of virus, including social distancing and mask-wearing.

Brazil has yearly influenza vaccine drives that target people above the age of 60, children, and other high-risk groups like health-care professionals. As a result, a relatively high rate of older Brazilians are vaccinated against the flu. The country has also given out enough coronavirus shots to immunize some 78 percent of its population, according to Reuters.

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