Covid-19 Measures Have All But Wiped Out The Flu In The Southern Hemisphere


 
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By David Luhnow and Alice Uribe

For the past two months, as winter descended on Chile, infectious-disease specialist Claudia Cortés worked tirelessly to keep a wave of critically ill Covid-19 patients alive in the hospital where she works. At the same time, she worried about what would happen when the usual wave of influenza patients arrived.

They never came.

From Argentina to South Africa to New Zealand, countries in the Southern Hemisphere are reporting far lower numbers of influenza and other seasonal respiratory viral infections this year. In some countries, the flu seems to have all but disappeared, a surprise silver lining that health experts attribute to measures to corral the coronavirus, like mask use and restrictions on air travel.

The decline could be good news for health officials in the U.S. and Europe worried about a possible second wave of coronavirus infections this fall and winter. Not only is the coronavirus more likely to spread as people gather indoors during cold weather, but it is also flu season, meaning hospitals could get a double whammy of influenza and Covid-19 patients, both of whom sometimes require intensive-care treatment.

Robert Redfield, director of the U.S. Centers for Disease Control and Prevention, has warned that the fall and winter could see both respiratory epidemics—Covid-19 and seasonal influenza—circulating side by side, overwhelming hospitals.

“I do think the fall and winter of 2020 and 2021 are going to be probably one of the most difficult times that we’ve experienced in American public health,” Dr. Redfield said in early July.

But the news from the Southern Hemisphere offers some hope. The decline isn’t just for flu, but for other respiratory viruses as well, such as respiratory syncytial virus, which largely affects children, and pneumococcal disease.

“We keep checking for the other viruses, but all we’re seeing is Covid,” said Dr. Cortés, the Chilean doctor. Of roughly 1,300 Covid-19 patients she has treated since late March, only a handful had the flu. “We were surprised by the decline in the other viruses like influenza. We never dreamed it would practically disappear,” she said.

Chile has recorded only 1,134 seasonal respiratory infections so far this year, compared with 20,949 during the same period last year. In the first two weeks of July—the equivalent to early January in the Northern Hemisphere and the height of the local flu season—the country reported no new confirmed influenza cases.

In the last two weeks of June, Australia registered only 85 new laboratory-confirmed influenza cases, compared with 22,047 confirmed cases for the two weeks through June 30 a year earlier, according to Australia’s National Notifiable Diseases Surveillance System.

In New Zealand, there are fewer hospitalizations than normal at this time of year, and the death rate has fallen.

“This [decline of other respiratory viruses] surprised me,” said Dr. Sylvain Aldighieri, deputy director of the Department of Health Emergencies at the Pan American Health Organization, the Western Hemisphere arm of the World Health Organization. “We were expecting a double burden of cases, because in countries like Chile and Argentina, the flu winter epidemic places a high burden on health-care services.”

Dr. Aldighieri, however, warned that without the strict containment measures taken by Southern Hemisphere countries, influenza would probably have returned as usual. He said hospitals and doctors in the U.S. and Europe should prepare for a normal flu season as their economies reopen and restrictions are lifted.

Many Southern Hemisphere countries took a range of steps to contain the coronavirus. Argentina, South Africa and New Zealand imposed strict lockdowns, while Australia allowed some businesses to stay open but restricted many others. Most countries banned large gatherings and closed schools, while citizens adopted frequent hand-washing, social distancing and wearing masks.

Restricting incoming air travel helped Southern Hemisphere countries block one traditional source of infection: travelers arriving from the Northern Hemisphere at the end of the northern flu season in March and April. Those travelers could infect people in the south, where it would spread as the weather chilled. Countries including Chile, Argentina, Australia and New Zealand have barred international arrivals since March.

“Strict border restrictions and alert-level-based response including social-distancing measures has had an impact,” said Dr. Sarah Jefferies, a public-health physician at New Zealand’s Institute of Environmental Science and Research, which monitors flu trends and provides data to the WHO.

Since the U.S. and Europe haven’t restricted international travel nearly as much, they will be more prone to having travelers import the flu, said Dr. Aldighieri.

Richard Medlicott, a general medical practitioner in a suburb of the New Zealand capital of Wellington, estimated the number of influenza patients had dropped at his clinic by 90% compared with last winter. For all types of respiratory illness the decline was about 60%, he said.

Dr. Medlicott said one big factor was having schools and child-care centers closed. “Children are the main reservoir [of these viruses],” he said. “They haven’t been at child care and that has meant they’ve had less chance to spread it in the community.”

Habits intensified by the pandemic such as hand washing and new behaviors such as coughing into the elbow also helped contain the spread of flu and other respiratory diseases, he said.

Some of these behaviors are likely to stick. Combined with increased use of medical consultations by video—away from doctors offices and hospitals where germs are prevalent—that could suppress the flu in subsequent years, said Dr. Medlicott, a former medical director of the Royal New Zealand College of General Practitioners.

Stepped-up vaccination for flu since the coronavirus pandemic began has also likely helped. Countries including Australia and Chile report far higher rates of vaccination than in previous years, as fears of coronavirus prompted elderly and other at-risk people to get the shots.

Evidence that steps like social distancing also slowed other respiratory viruses first emerged in the Northern Hemisphere in March, when the traditional flu season ended earlier than expected in countries ranging from Japan to the U.S.

In Australia, influenza cases usually begin rising in March, April and May. Then, in June, “things really start to get going,” said Professor Ian Barr, deputy director of the WHO Collaborating Centre for Reference and Research on Influenza at the Doherty Institute for Infection and Immunity, a nonprofit research center in Melbourne.

But instead, the number of influenza cases has tapered off, from around 15% of the five-year average in March to just 4% of the five-year average in June, he said. In Australia, confirmed flu cases plunged 84% to 20,739 from the beginning of January to June 30, compared with 132,424 during the same period the previous year.

Dr. Rod Pearce, an Australia-based general practitioner who also works at a Covid-19 testing clinic near Adelaide, said his clinic has found only one positive flu case out of around 1,000 tests done so far.

In Argentina, the number of laboratory-confirmed flu cases fell 64% to 151,189 from January through early July, compared with an average of 420,737 during the same period the previous five years, according to government figures.

“Covid has displaced all the other viruses, which makes me certain that it is far more transmissible,” said Dr. Gustavo Lopardo, an infectious-disease specialist and professor at the University of Buenos Aires.

Even in countries that have struggled to contain the virus, like Brazil, the winter flu season was far more mild. Brazil has had more than 80,000 coronavirus-related deaths, but saw flu cases fall by about 40% and flu deaths by half.

In South Africa, which has been under a strict lockdown for three months, there were never enough flu cases to say a seasonal epidemic had begun, say doctors there.

“We are certainly pushing the bounds of when it should have started now so I think it’s correct to assume that this is a real phenomenon,” said Richard Lessells, an infectious-disease specialist at the University of KwaZulu-Natal.

The country of 60 million people usually sees some 50,000 severe flu cases a year, leading to around 12,000 deaths. Dr. Lessells said the low number of flu infections this year was likely due to steps to prevent the spread of the coronavirus and a government push for people to get the flu vaccine.

New Zealand’s flu-surveillance program indicates only 0.7% of the population had influenza-like symptoms such as fever and cough in the first week of July, a fraction of the 3.0% to 4.3% range for the previous two years in June and July. The decline has meant lower than normal hospitalizations overall, even with coronavirus patients counted.

In the Auckland region, the weekly hospitalization rate was down to two people per 100,000 by mid-July compared with the long-term average of 8.5 for this time of year. It is also the lowest since a tracking program for acute respiratory infections began in the Auckland region in 2012.

For influenza itself, there have been zero hospitalizations in the Auckland region—home to a third of New Zealanders—since late March.

Deaths have also fallen, by about 5% in the first half of the year compared with the previous year and are also down from 2018 and 2017. Researchers at the University of Otago said the reduced deaths are “unlikely to be a chance finding” and could be linked to several factors stemming from the lockdown, including lower levels of respiratory illness, fewer road crashes, reduced air pollution and a decline in fatal work accidents.

However, the researchers said it is possible deaths will rebound later on due to factors such as delayed cancer treatment and higher unemployment, which is associated with increased suicide and cardiovascular disease.

And in New Zealand, which has lifted virtually all coronavirus restrictions, Dr. Jefferies cautioned that there were still a few more months of winter and spring left and that greater economic activity could lead to an uptick in influenza in coming months, especially if people get careless about social distancing.



 
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