This season’s primary strain of H1N1 is becoming overshadowed by new H3N2 cases according to health officials.
The H3N2 strain is more deadly and was responsible for last year’s epidemic that claimed 80,000 lives.
For the week ending Feb. 16, 2019, the CDC reports the following:
The percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories increased. While influenza A(H1N1)pdm09 viruses predominated in most areas of the country, influenza A(H3) viruses have predominated in HHS Region 4 and accounted for 47% of subtyped influenza A viruses detected nationally during week 7. During the most recent three weeks, influenza A(H3) viruses were reported more frequently than influenza A(H1N1)pdm09 viruses in HHS Regions 6 and 7 and influenza A(H1N1)pdm09 and influenza A(H3) viruses were reported in approximately equal numbers in HHS Region 2.
“It looks like we are moving from an H1 wave to an H3 wave,” said Lynnette Brammer, lead of CDC’s domestic influenza surveillance team. “There’s still a lot of flu to come.”
Fortunately the strains show susceptibility to antiviral medications such as oseltamivir and peramivir.
It’s not uncommon for various strains of flu to case illness during a single flu season.
Last week, the CDC reported a mid-season efficacy rate of 47% for this year’s flu shot, up from 36% estimated efficacy last year. However this may change in light of these new reports.
In a good year flu shot efficacy may be 65%. It’s difficult to reach higher numbers as viral flu strains mutate easily and immune systems of the general public are so varied. Per the CDC the flu shot during the 2010-2011 flu season was one of the most effective.
This year the predominant flu strain was H1N1, in contrast to the more wily H3N2 which evaded being a sharp match for last year’s flu vaccine. However, now that H3N2 is making the rounds, we could see a drop in our flu vaccine efficacy.
They report the following:
Interim estimates of vaccine effectiveness based on data collected during November 23, 2018–February 2, 2019, indicate that, overall, the influenza vaccine has been 47% (95% confidence interval = 34%–57%) effective in preventing medically attended acute respiratory virus infection across all age groups and specifically was 46% (30%–58%) effective in preventing medical visits associated with influenza A(H1N1)pdm09 (6).
It is not too late to get the flu shot and medical providers are still recommending vaccination.
According to the CDC “preliminary cumulative in-season prevalence estimates indicate that influenza has caused 155,000–186,000 hospitalizations and 9,600–15,900 deaths.”
To date, 28 children have died this year from flu related illness.
Flu season peak is still occuring as winter appears to more severe this year, hence numbers can rise.
The Flu – Your Questions Answered
When does flu season begin and how long does it last?
Flu season has begun already. It typically starts in the Fall, and ends late Spring. So the range is described as October to May with it peaking December to March.
How bad will this flu season be?
It is difficult to predict, but already this early in the season we’ve had multiple flu related deaths reported by the CDC’s Flu View.
What is the flu? How can one die from it?
The flu is caused by a virus. Multiple strains of virus’ can cause the flu. The virus itself can be lethal, however the greatest risk comes with what it does to your immune system, thereby putting one at risk of secondary infections. Pneumonia is the number one cause of flu-related deaths. Secondly, it can exacerbate existing conditions such as asthma, seizures, even promote preterm birth, hence those who are pregnant or have preexisting medical conditions are urged to get vaccinated against the flu. Moreover those who qualify should get the pneumonia vaccine as well.
What does this year’s flu vaccine cover?
According to the CDC, the trivalent vaccine covers for these three strains of flu virus:
- A/Michigan/45/2015 (H1N1)pdm09–like virus
- A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus
- B/Colorado/06/2017–like virus (Victoria lineage)
Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013–like virus (Yamagata lineage).
These vaccines are aimed at providing protection against the Swine flu, and some influenza A and B strains.
What about older individuals?
This year, those over 65 will have three options for their flu vaccine.
Fluzone High-Dose – a higher dose flu vaccine that will hopefully allow their immunity to protect against the flu longer
FLUAD – the trivalent flu vaccine with an adjuvant to stimulate more of an immune response.
Flublock Quadrivalent – provides protection against 4 strains.
What about the nasal spray vaccine?
This year, the CDC allows use of the nasal spray vaccine as it has shown to have improved efficacy from prior years. However it is only recommended for those who are between the ages of 2 and 49 and cannot be given to those who are pregnancy or who have compromising medical conditions as outlined by the CDC.
Who should get the flu shot?
All individuals 6 months old and older unless specified by their medical provider.
What if I’m allergic to eggs?
Most individuals allergic to eggs can still get the flu vaccine, but if the allergy to eggs is severe (anaphylaxis, angioedema, difficulty breathing), the CDC recommends notifying your medical provider and being in a facility to monitor you if you do get the flu vaccine.
Will I get the flu from the flu shot?
No. The flu vaccine has a “killed” version of the virus meaning it’s not an active virus (as opposed to a live attenuated vaccine, a weakened down version of it). A “killed” or “inactivated” vaccine merely has the pathogen particles to induce an immune response. Additionally, when one states they got the flu despite the flu shot it could be that the flu shot only protects against 3 – 4 strains and they were infected with a more rare strain not covered by the vaccine.
How effective is the flu vaccine?
The average effectiveness each year hovers around 60%. Last year’s efficacy was much lower and this year’s has not been predicted as of yet. Australia is still reporting active cases on their Department of Health website.
I feel sick after the flu shot, why?
For some, the immune response that ensues can make one feel mildly ill, but should not resemble the flu. Those who state they got the flu “immediately” after receiving the shot, might have already been exposed and had not had a chance to produce immunity prior to their exposure.
What are symptoms of the flu? How is it different from a cold?
A cold comes on slower and less severe. Flu symptoms are more abrupt and can include:
- Body Aches
- Sore Throat
- Shortness of Breath
Are there medications to treat the flu? Will antibiotics work?
There are antiviral medications available, such as Tamiflu, to treat the flu. Antibiotics, however, will not work since the flu is not caused by a bacteria but rather a virus. However if a secondary bacterial infection takes over, antibiotics may be used.
How can I prevent getting the flu?
Besides vaccination, avoid being around those who are sick, thorough hand washing, and take good care of yourself. A balanced diet, exercise and sleep regimen can help boost your immune system.