Influenza is affecting many people in North Central Washington this year and the number of infections over the last three weeks has really increased. So, what is influenza, what are the usual symptoms, what symptoms separate it from other infections, how long does it last, when should you seek medical attention, and what should you do to reduce your chances of getting it?

The only predictable thing about influenza is that it is unpredictable. There are two major types of influenza: seasonal and pandemic. Unlike other viruses that we have vaccines for — like measles — the flu virus changes a little bit every year. As a result, there are always going to be seasonal flu outbreaks every single winter, and a new vaccine has to be made every year to provide the best possible protection.

Every once in a while, the flu virus changes a great deal, and this is when catastrophic pandemics occur. The pandemic flu of 1918 killed 50 million to 100 million persons worldwide, and much less serious pandemics occurred in 1957, 1968 and 2009.

Because seasonal flu happens every year, we are accustomed to the notion of influenza, and it’s easy to underestimate its severity.

While flu tends to be more severe especially amongst the very young, the very old, pregnant women, and individuals with impaired immune systems or underlying lung disease, severe disease can happen to anyone. During last year’s flu season across the U.S., about 35 million people became ill with influenza; half a million were sick enough to be hospitalized, and about 35,000 people died from the flu.

Flu seasons can be unpredictable, which causes the vaccine’s effectiveness to vary year to year. Typically, the flu vaccine helps reduce flu-related hospitalizations by about 100,000 Americans per year, and reduces the risk of flu death in children. This year, most cases so far have been influenza B, and have occurred almost entirely amongst individuals who didn’t get this year’s vaccine. We are now starting to see Flu A cases.

There has also been a nasty common cold virus (due to rhinovirus) as well as RSV (Respiratory Syncytial Virus) — typically causing asthma-like symptoms and breathing problems in young children — circulating in NCW.

Differentiating the flu from the common cold can be difficult at first. The typical symptoms of flu include sudden onset of fever greater than 100.3 F and headache, malaise, muscle aches, dry cough, sore throat or nasal congestion. Unlike the common cold, however, people often describe the flu as “feeling like I have been hit by a truck.” The symptoms of common cold tend to be more gradual, often with more earache and sinus pain, and when fevers are present tend to be relatively mild.

Complicating our ability to differentiate these viral respiratory illnesses are the novel viruses that arise from certain parts of the world every few years. This includes several new coronaviruses that have arisen: SARS in 2003 in Southeast Asia, MERS in 2012 in the Middle East, and the 2019 novel coronavirus from Wuhan province in China. The first imported case to the U.S. of this current coronavirus outbreak was reported this month in a Snohomish County resident who had just traveled to Wuhan Province.

The initial severe symptoms of flu — including fever — typically last for 3-5 days, but cough, fatigue and mild weakness can persist up to 10-14 days. You are contagious starting one day prior to onset of symptoms for 5-7 days. The virus is primarily transmitted from the respiratory tract (eg. breathing in virus that is sneezed or coughed into the air from an ill individual), but it can also be transmitted from touching contaminated surfaces. This is why frequent hand washing with either soap/water or alcohol-based hand sanitizers during flu season is critical.

Flu is a virus, so it doesn’t respond to antibiotics. An antiviral called Tamiflu (Oseltamavir) can be used to treat influenza, but it has limitations. It tends to reduce the risk of complications from flu and on average decreases duration of symptoms by 1-2 days. It is typically not recommended for those who have had symptoms for more than 48 hours already, except in certain populations whom are at higher risk of complications.

For individuals who are otherwise healthy and have the typical influenza symptoms, if the duration is less than 48 hours since onset and you wish to consider taking Tamiflu–then contact your physician’s office or go to a walk-in clinic. Otherwise, symptomatic treatment with Tylenol for fevers and aches is OK. If your symptoms are outside of the typical (fever greater than 103.5 F, worsening shortness of breath, chest pain, persistent nausea or vomiting causing inability to drink adequate fluids) or if you begin to get better but then have worsening respiratory symptoms and recurrence of fevers, then you do need to be seen and evaluated.

For “higher risk” patients, including patients 65 or older or under the age of 2 and those with active cancer or immunosuppression, contact your physician’s office about whether you need to be seen.

Dr. Mark Johnson is an infectious disease specialist at Confluence Health.