Virus World

In 2017, a terrible flu season in Australia presaged an American outbreak in which 79,000 died. Experts advise getting the shot soon. Australia had an unusually early and fairly severe flu season this year. Since that may foretell a serious outbreak on its way in the United States, public health experts now are urging Americans to get their flu shots as soon as possible.

“It’s too early to tell for sure, because sometimes Australia is predictive and sometimes it’s not,” said Dr. Daniel B. Jernigan, director of the influenza division of the Centers for Disease Control and Prevention. “But the best move is to get the vaccine right now.” The number of cases of flu in this country is still quite low, according to the weekly C.D.C. FluView released Friday. But as the weather cools, it is expected to ramp up. In 2017, Australia suffered its worst outbreak in the 20 years since modern surveillance techniques were adopted. The 2017-2018 flu season in the United States, which followed six months later as winter came to the Northern Hemisphere, was one of the worst in modern American memory, with an estimated 79,000 dead. 

This year’s Australian outbreak began in April, two months earlier than usual, and persisted into October. Alarming early reports  said the number of deaths might surpass those in 2017, but that did not quite happen. (The country did have more positive flu tests than ever before, but that was in part because far more tests were performed.). Nonetheless, there were more flu-related deaths than usual, while hospitalization rates and nursing home outbreaks “were at moderate to high levels,” said  Ian Barr, deputy director of World Health Organization Collaborating Center for Reference and Research on Influenza in Melbourne.  Direct comparisons of mortality rates are difficult, because Australia counts only deaths in which a hospital declares influenza the cause; there were 662 this year, and 745 in 2017. Not only is the United States population 13 times bigger, but the C.D.C. — aware that flu triggers even more deaths from pneumonia, sepsis, heart attack and other illnesses — looks at the increased death rates from many illnesses in bad flu years, and calculates how many were probably due to influenza.

At the peak of the 2017-2018 season, the C.D.C. estimated that more than 56,000 Americans would die. Officials later calculates that  79,000 had— which, the agency noted, is more people than usually fill a Super Bowl stadium.  In 2017, Australia’s deadly season set off alarm bells in Britain, where tabloids featured headlines about the "killer Aussie flu".  But no such dire warnings were issued to Americans, in part because of turmoil at the C.D.C. and its parent agency, the Department of Health and Human Services. 

Last month, Dr. Price’s successor, Alex M. Azar II, also got a flu shot on camera at a news conference   that National Foundation for Infectious Diseases holds every year to urge Americans to get vaccinated. Mr. Azar — who stayed through the question and answer session — made it clear that the Trump administration is firmly behind vaccination......

The dominant flu strain circulating the world appears to have changed since the World Health Organization decided which one to base shots on in February, a Canadian flu expert warns. 

• Flu circulates the world annually and becomes active in the US around October
• WHO scientists chose the forms of the virus to base vaccines on in February for the Northern Hemisphere and this month for the Southern Hemisphere
• Last week the WHO predicted different strains of the flu would be dangerous to the Southern Hemisphere from the ones they based Northern shots on 
• That may mean the North's shot will be 'mismatched' 
• A mismatched vaccine for influenza A/H3N2 is partially blamed for the record deaths from the 2017-2018 flu season  

This year's flu vaccine may not be effective, a top expert warns.  Dr Danuta Skowronski, an influenza expert from the University of British Columbia told Stat News that the this year's flu shot for the Northern Hemisphere - including the US, UK and Canada - is likely to be a 'mismatch.'  Flu shots have to be newly developed ahead of each season based on scientists' predictions of which strains will be most active in the coming months.  Officials from the World Health Organization (WHO) choose the strains for the Northern Hemisphere's shot in February, and chose those for the Southern Hemisphere last week. 

For the Southern Hemisphere, officials chose influenza A/H3N2 and B/Victoria - different ones from the strains picked for the North, suggesting to Dr Skowronski that the prior prediction was wrong and the Northern shots may be ineffective.  

'I think the vaccine strain selections by the WHO committee are obviously important for the Southern Hemisphere but they’re also signals to us because they’re basing their decisions on what they see current predominating on the global level,' said Dr Skowronski.   Every year, the flu virus makes its way around the world, typically becoming more active in the US in October.  Without fail, between three and five million people fall ill globally and anywhere between 290,000 and 650,000 die of the disease.  Most of those that die are very young, very old or have an underlying condition.  But in the worst flu seasons, a healthy people succumb to the virus as well.  Already, one child has died of the flu in the US - an alarming bellwether that the US may be in for a particularly bad season.   The 2017-2018 flu season was one of those particularly nasty years for the flu.  More than 80,000 people died of flu in the US that season, including 160 children. 

It was the highest death toll since 1976, and pediatric deaths set an all-time record, aside from pandemics like the 1918 Spanish flu, which killed between 20 and 100 million worldwide. The historically high fatality rate from the 2017-2018 flu season was largely blamed on the fact that the flu shots distributed to the US were a poor match for the circulating strains of the virus. Flu vaccines are the best protection there is against the flu - but they are only effective against the strains of the virus upon which they're based - and that's a matter of calculated guesswork.

It's impossible to quantify exactly how many strains of flu there are. The most common viruses are influenza A and B, but there are others, they vary based on the hosts they first attack (swine, bird etc) and mutate frequently. 

Ahead of each season, health officials and flu experts the world over convene to carefully examine early cases of the flu in each season and the patterns from the previous years to predict which strains and variations will be dominant that year.  Flu vaccines are then developed based on either a dead form of those viruses or partial viruses.  When scientists' predictions are close, the vaccines are highly effective, and fewer people die - so long as vaccination rates remain high. When they're off-base, illnesses surge and death tolls climb. These predictions are tricky, as the strains of the virus vary from continent-to-continent and the ways they move from one to the other vary annually.  But typically, the most potent and common ones are similar in the North and South.   Flu season starts earlier in the year in the Northern Hemisphere, so WHO officials convened in February to decide what strains should be the basis of the Northern shot. After narrowing down the viruses to influenza B/Victoria and A/H3N2, the scientists struggled to make a choice about which particular variation of the H3N2 virus would pose the greatest threat in the 2019-2020 flu season, Stat reported. 

So they went with the virus type that had suddenly ramped up at the end of last season in the US.  But Dr Skowronski thinks that that might have been a mistake.  'That H3N2 wave was late and it was evolving at the time that they met in February,' Skowronski said. 'And there was a diverse mix of H3 viruses. And it wasn’t clear to them, I guess, [which strain] … would emerge the clear winner,' she told Stat.  But by the time the officials met again this month to decide the basis for the Southern Hemisphere's shot, things had changed.  H3N2 has posed a shot-matching challenge in recent years. It was the same virus that the 2017-2018 shots offered such little protection - only about 40 percent - against that season's dominant, and particularly aggressive strain. Dr Skowronski would like to see the Northern Hemisphere's shot re-formulated, based on the Southern Hemisphere shot.  But shorty of that, she urges that doctors be prepared that even people who get inoculated against the flu may wind up contracting it this year any way.  At least, however, the influenza B virus predicted in February appears to still be the correct one, which is particularly important as children tend to contract and die from B strains more often.   Last week, officials from the World Health Organization chose the strains of the virus upon which to base the Southern Hemisphere's vaccine 

Strains recommendations available at the WHO site: https://www.who.int/influenza/vaccines/virus/recommendations/en/