While some folks still believe that the flu is a mild infection, most people understand that the flu is a very dangerous disease.
A dangerous disease that kills hundreds of children and tens of thousands of adults each year in the United States.
Who Dies from the Flu?
In addition to thinking that the flu isn’t dangerous, some folks misunderstand just who is at risk for dying from the flu.
While it is certainly true that some people at higher risk than others, including those who are very young, very old, and those with chronic medical problems, it is very important to understand that just about anyone can die when they get the flu.
Just consider the 2017-18 flu season, in which 181 children died.
In addition to the fact that half of the kids who died were otherwise healthy, without an underlying high risk medical condition, it is important to realize that up to 80% were unvaccinated.
You want some time for it to start working, so that you can be sure that you are protected.
So while some folks talk about getting a flu vaccine too early, you do want to make sure that you get it in time to get protection before flu is active in your area. Still, it is never too late to get a flu vaccine. It is better to get a flu vaccine late in the flu season than to skip it all together.
What about younger kids getting their flu vaccine for the first time and who need 2 doses? When do they start getting protection?
“The first dose “primes” the immune system; the second dose provides immune protection.”
Study Looks at Flu Vaccine Dosing in Children
Although they likely have some protection after that first dose, the best protection will begin 10 to 14 days after their second dose.
It seems like every year we get early reports of the start of flu season.
Because a few people had positive flu tests somewhere…
Is Flu Season Starting Already?
While there are many things about the flu that are unpredictable, including when flu season will start, peak, and end, there are some things that have become rather routine.
One of the things that we have come to expect every year is folks declaring an early start to flu season.
Not surprisingly, they are usually wrong.
So why do some folks test positive in August or September if it isn’t because flu season is starting?
“During periods when influenza activity is low and there is low influenza virus circulation among persons in the community, the positive predictive value of influenza tests is low (that is, the chance that a positive result indicates that the patient has influenza is low – consider potential for a false positive result), and the negative predictive value is high (the chance that a negative result indicates that the patient does not have influenza is high – likely true negative result ).”
CDC on the Algorithm to assist in the interpretation of influenza testing results and clinical decision-making during periods when influenza viruses are NOT circulating in the community
When flu activity is low, such as it is during the summer or early fall before flu season has really started, you have a higher chance for a false positive flu test. So even though you have cold or flu symptoms and a positive rapid flu test, you might not really have the flu. The test is falsely positive. It’s wrong.
“Influenza prevalence varies between and within seasons. On the basis of our estimates, rapid tests are of limited use when prevalence is <10%”
Grijalva et al on Accuracy and Interpretation of Rapid Influenza Tests in Children
While other, more accurate flu tests are available, they are more expensive and take longer to process and get results. And since the diagnosis of the flu is often made clinically anyway, classic flu signs and symptoms during flu season, you typically don’t need a flu test unless being admitted to the hospital or if the results will really change how you are being treated.
While flu season usually starts in October, it is the peak that we are usually more concerned about. That’s when you are most likely to be exposed to someone and get the flu.
When does flu season usually peak?
It depends, but usually sometime between December and March, typically in February. Getting back to how unpredictable flu season can be, there have been a few times that flu season has peaked as early as October though.
How can you reduce your chances of having a false positive flu test?
Everyone should get a flu vaccine each year, as long as they are at least six months old and have no true contraindications.
That has been the recommendation since at least the 2010-11 flu season.
And while most kids get vaccinated, not all do.
Are Your Kids at High Risk for Flu Complications?
There are some kids, those at high risk for flu complications, who definitely shouldn’t skip or delay their flu vaccine.
all children aged 6 through 59 months (younger than age 5 years);
children who have chronic medical conditions, including pulmonary (such as asthma and cystic fibrosis), cardiovascular (excluding isolated hypertension), genetic (Down syndrome), renal, hepatic, neurologic (cerebral palsy, epilepsy, stroke, muscular dystrophy, and spina bifida, etc.), hematologic (sickle cell disease), or metabolic disorders (including diabetes mellitus and mitochondrial disorders);
children who are immunocompromised due to any cause (including immunosuppression caused by medications or by HIV infection);
teens who are or will be pregnant during the influenza season;
children and adolescents (aged 6 months through 18 years) who are receiving aspirin- or salicylate-containing medications (like for Kawasaki disease) and who might be at risk for experiencing Reye syndrome after influenza virus infection;
residents of nursing homes and other long-term care facilities;
American Indians/Alaska Natives;
children who are extremely obese (body mass index ≥40).
You also shouldn’t skip or delay getting a flu vaccine if your:
kids are household contacts of children aged ≤59 months (i.e., aged <5 years) and adults aged ≥50 years, particularly contacts of children aged <6 months;
kids are household contacts of someone with a medical condition that puts them at higher risk for severe complications from influenza.
Again, since everyone should get a flu vaccine, these higher risk classes shouldn’t determine whether or not you vaccinate your kids, but they might influence the timing.
Again, don’t skip your child’s flu vaccine because they aren’t in a flu high risk group.
In most flu seasons, about 80% of children with the flu who die are not vaccinated. And many of them will be otherwise healthy, without an underlying high risk medical condition.
Get your child vaccinated against the flu. And if they are in a high risk group, make sure you do it well before flu season starts and maybe as soon as flu vaccine becomes available in your area.
News like that and folks getting exposed to other infectious diseases, probably has them wondering just how contagious these diseases are. Do you have to be sitting next to someone to get them? In the same row? On the same floor?
Understanding Your Risk of Catching a Disease
Fortunately, most diseases are not terribly contagious.
We worry about some things, like SARS and Ebola, because they are so deadly, not because they are so contagious or infectious.
Wait, contagious or infectious? Aren’t they the same thing?
To confuse matters, some infectious diseases aren’t contagious, like Lyme disease. And some vaccine-preventable diseases are neither infectious nor communicable. Think tetanus. You may have never thought of it that way, but you aren’t going to catch tetanus from another person. Of course, that’s not a good reason to skip getting a tetanus shot!
To understand your risk of getting sick, you want to understand a few terms, including:
infectious disease – a disease that can be transferred to a new host
communicable – an infectious disease that can be transferred from one host to another
non-communicable – a non-infectious disease which can not be transferred from one host to another
contagiousness – an infectious disease that is easily transferred from one person to another
infectivity – the ability of an infectious agent to cause an infection, measured as the proportion of persons exposed to an infectious agent who become infected. Although this doesn’t sound much different from contagiousness, it is. The Francisella tularensis bacteria is highly infectious, for example, to the point that folks exposed to a culture plate are given antibiotics or put on a fever watch. Few of us get tularemia though, because transmission is through tick bites, hunting or skinning infected rabbits, muskrats, prairie dogs and other rodents, or inhaling dust or aerosols contaminated with F. tularensis bacteria. So if you get exposed, you will probably get sick, but there is a low probability for getting exposed.
incubation period – the time it takes to start having symptoms after you are exposed to an infectious disease. A longer incubation period increases the chances that someone will get exposed to a disease and travel home before getting sick. A shorter incubation period, like for influenza, means that a lot of people can get sick in a short amount of time.
contagious period- the time during which you can spread the illness to other people and may start before you have any symptoms
quarantine – used to separate people who have been exposed to a contagious disease and may become sick, but aren’t sick yet
isolation – used to separate people who are already sick with a contagious disease
transmission – how the disease spreads, including direct (direct contact or droplet spread) vs indirect transmission (airborne, vehicleborne, or vectorborne)
R0 (r nought) – the basic reproductive number or the number of new infections originating from a single infectious person among a total susceptible population
Rn – the net reproductive number, which takes into account the number of susceptibles in a community
infectious period – how long you are contagious
Got all that?
How Contagious Is Measles?
If not, understanding how easily you can get measles should help you understand all of these terms.
Measles is highly contagious, with a very high R0 number of 12 to 18.
the measles virus can live for up to two hours on surfaces and in the airspace where an infected person coughed or sneezed
infected people are contagious for up to four days before they have a rash and even know that they have measles, so expose lots of people even if they get put in isolation once they get diagnosed
infected people continue to be contagious for up to four days after the rash appears, so can continue to expose people if they aren’t put in isolation
So you don’t need to have someone with measles coughing in your face to get sick. If they coughed or sneezed at the grocery store, on the bus, or at your doctor’s office and then you entered the same area within two hours, then you could be exposed to the measles virus and could get sick.
As we continue to see outbreaks of vaccine-preventable diseases in the post-vaccination era, it is important that these outbreaks be quickly contained.
But it is important to understand that these outbreaks don’t simply stop on there own. A lot of work goes into containing them.
Working to Contain an Outbreak
And that work containing outbreaks is expensive. Much more expensive than simply getting vaccinated.
For example, the total personnel time and total direct cost to the New York City Department of Health and Mental Hygiene responding to and controlling the 2013 outbreak in NYC were calculated to be at least $394,448 and 10,054 personnel hours.
Why it is so expensive is easy to see once you understand all of the work that goes into containing an outbreak. Work that is done by your local health department as soon as a case of measles, or other vaccine-preventable disease, is suspected.
Work that, for a measles outbreak for example, includes:
initiating a case and contact investigation
quickly confirming that the patient actually has measles, including testing
assessing the potential for further spread – identifying contacts who aren’t immune to measles and are at risk for getting measles
isolating people with measles and quarantining contacts who aren’t immune to measles for at least 21 days after the start of the measles rash in the last case of measles in the area, including everyone who is intentionally unvaccinated
having targeted immunization clinics in the affected population, such as a school or church, to get as many people vaccinated as possible, even after 72 hours, so they have can be protected in the future
That’s an awful lot of work.
Work that continues until the outbreak officially ends.
Finding the Source of an Outbreak
Another big part of the work that goes on to contain an outbreak is identifying the source of the outbreak.
Was it someone who had recently been traveling overseas, a visitor from out of the country, or someone that was already part of an another outbreak?
Why is that so important?
If you don’t find the source of the outbreak, then you can’t be sure that you have found all of the people that have been exposed, and the outbreak might go on for an extended period of time.
A week after returning home from the trip, he gets sick, but returns to school after a few days. He then develops a rash and sees his family physician, followed by his pediatrician, and then makes a trip to the emergency room because he continues to have a high fever and rash (classic measles symptoms).
He is eventually diagnosed with measles, but not before eleven other children are infected with measles. This includes two of his siblings, five children in his school, and four children who were exposed at his pediatrician’s office.
It is not as simple as that though.
During this measles outbreak:
Three of the children who became infected were younger than 12 months of age, and were therefore too young to have been vaccinated
Eight of the nine children who were at least 12 months old were intentionally unvaccinated because they also had personal belief vaccine exemptions
About 70 children were placed under voluntary quarantine for 21 days after their last exposure because they were exposed to one of the measles cases and either didn’t want to be vaccinated or were too young
One of the infants with measles traveled to Hawaii, raising fears that the measles outbreak could spread there too
All together, 839 people were exposed to the measles virus.
At least one of them was a 10-month-old infant who got infected at his well child checkup, was too young to have gotten the MMR vaccine yet, and ended up spending three days in the hospital – time his parents spent “fearing we might lose our baby boy.”
The parents of this 10-month-old weren’t looking for a vaccine exemption and didn’t want their child to catch measles, a life-threatening, vaccine-preventable disease. Instead, they were counting on herd immunity to protect him until their child could be protected with an MMR vaccine. They were one of “those who come into contact with them” that got caught up in a decision of some other parents to not vaccinate their child.
The kids who are at risk and get a vaccine-preventable disease because they are too young to get vaccinated, have an immune system problem that prevents them from getting immunized or their vaccine from working, and the kids who simply didn’t get protected from a vaccine are the hidden costs of these measles outbreaks that we don’t hear about often enough.
What to Know About Finding the Source of an Outbreak
Without all of the hard work that goes into containing outbreaks, the outbreaks of measles, pertussis, mumps, hepatitis A, and other vaccine preventable diseases would be even bigger.
Anti-vaccine folks rarely talk about the complications of vaccine-preventable diseases. For that matter, they also often push the idea that vaccines don’t even work and that these diseases aren’t even vaccine preventable, don’t they?