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| Comparing Epi Week 13 Flu Levels - South Australia |
#13,991
Australia's winter flu season usually doesn't get started until June, and generally peaks in late July or August. As the chart above illustrates, at Epi Week 13, flu activity in Australia is expected to be practically nil.
Except this year, it isn't.In fact, Australia has been reporting an unusual number of `summer flu cases' for the past few months (see March 5th Virology Down Under Blog by Dr. Ian Mackay), although it wasn't clear at that time whether this increase was due to more comprehensive testing or a change in the level of viral activity.
Overnight the Australian media has been filled with reports warning of an early, and possibly severe, flu season ahead. A few headlines include:
Flu vaccine program brought forward as surge in cases surprises health authorities
Could Australia be headed for its worst flu season on record?The most recent Weekly epidemiological summary (PDF 159KB)
Urgent flu vaccines rolled out in SA to combat surge in illnesses
from the South Australian Health agency reads:
InfluenzaWhile it is too soon to predict what kind of flu season Australia will face, one concern will be which subtype will dominate his year, as the H3N2 component of their vaccine - which was selected last September - has already been replaced in next fall's Northern Hemisphere vaccine, due to the rapid rise of clade 3C.3a.
From 1 January to 30 March 2019, there were 3,472 notifications of influenza reported to the Communicable Disease Control Branch, compared to 1,082 cases reported for the same period last year. Of these notifications:
- 1,889 were in females and 1,583 were in males
- the age range is 0 - 101 years, with a median age of 35 years
- 3,276 cases (94%) were due to influenza A and 196 cases (6%) were due to influenza B
- 157 cases (5%) were reported to have required hospital admission
- One case (0.03%) was reported to have died from influenza (89 years).
The most recent analysis of Southern Hemisphere flu viruses, released by WHO on April 1st, suggests that H3N2 viruses are gaining ground over H1N1, although it isn't clear how much is due to clade 3C.3a.
Today's blog is a reminder that while there are some expected rules of behavior for seasonal flu, the flu virus isn't obliged to follow them.
For a look back at non-pandemic flu season that really went off the rails, you may wish to revisit:
Remembering 1951: The Year Seasonal Flu Went Rogue
