We are finishing up on week 7 of the new year and about halfway into the 2018-2019 flu season. This season has been mild on account of less influenza case burden.  The 2017-2018 season was more severe than the current season. By the end of that April 2018, more than 34 million people had the flu, about 1 million were hospitalized, and approximately 54,000 people died.   However a mild case load doesn’t mean that the disease is any milder. The Center for Disease Control (CDC) estimates that from October 1, 2018 through to February 9, 2019 there have been an estimated 15-18 million cases of flu illnesses in the United States, 7-8 million have been seen in the clinic, an estimated 200,000 people required hospitalization, and around 11,600 to 19,100 people died from the flu.  These deaths are usually from a secondary bacterial infection, complications of respiratory distress, or a cardiovascular complication attributable to influenza.

As a general estimate, around 5-15% of the total US population gets the flu yearly. The hospitalization rate is 1 in 100 (1%) and the death rate is 1 in 1000 (0.1%). The highest risk of mortality is seen in the 65 and older age group, but almost 60% of reported hospitalization are ages of 18-64 years. Sure, most people will get a mild case of influenza and many people will get a classic case – with rapid onset of tiredness, body aches, chills and fever with cough, fewer will need to be hospitalized and a small percentage will die. Given the sheer magnitude of those affected, this means a lot of people. Influenza is not a mild illness.

With the attack rate of influenza approaching 20% and disease now widespread, we are approaching the peak of the flu season and greatest risk to acquire the infection. The good news is that if you have received the vaccine, you have a good chance that you will be either protected from the disease or get a milder case. This year’s vaccines were a good match with the selected viruses for the vaccine being the current active viruses (H1N1 pdm 09 (75-80%), H3N2 (20-25%)). The CDC estimates that the vaccine efficacy this year is 47%, approximating 61% in ages 7 months to 18 years, and probably lower in the over 50 age group.

In general, the vaccinations consist of two type of influenza viruses. Type A viruses are named after cell membrane (the outer layer of a virus) components – called hemagglutinin (H) and neuraminidase (N). The vaccine consists of 2 type A viruses H1N1 pandemic 2009 and H3N2. The type B viruses are named after two lineages B/Yamagata and B/Victoria. These are typically the strains that are included in a typical quadrivalent vaccination (4) or trivalent (minus Yamagata). Unfortunately, unlike the measles or other childhood viruses, there is more virus differentiation — changes known as antigenic drift, when gradual, or antigenic shift, when sudden. A new vaccine has to be decided upon each year. An extensive vetting occurs involving input from multiple centers, where the most common strains are selected. Occasionally, the vaccinations do not match the years prominent strains. This year, the majority of cases have been caused by the H1N1 pdm 09. Why not 100% effective — there are enough differences from the vaccine strains and the seasonal strains (yes – it changes/re-assorts that fast) that make an immune response from the vaccination not as effective.

Below are some general questions and answers regarding influenza:

1. Is it too late to get the vaccine if I missed earlier?  No. It is not too late to get vaccinated. The flu season usually tapers off after April. Getting a flu vaccination now would provide some protection for the remaining 2+ months. If you don’t want to make an appointment with your doctor, you can get it at many pharmacies. I would recommend the recombinant vaccination (quadrivalent) and the high-dose if you are older than 64.
2. How is the flu spread? What are the signs and symptoms of the flu and how do these differ from the common cold.

The influenza virus can be transmitted fairly easily in both coarse/large and fine respiratory droplets – the greater density of virus is on the smaller droplets. You can breathe these droplets in or put them in your mouth. There are several ways to put these in your mouth: Surface they can land on a surface and you can touch it and then put your fingers in your mouth or touch the food you then eat; Person-to-person a person could cover their cough and sneeze and shake your hands and… and Fomite, a person can contaminate an inanimate object, such as a doorknob, keys and a cell phone, and you can touch it and…

Unlike the cold, most people with the flu will get symptoms fairly abruptly. These will be fatigue and muscle aches. Cough is the most common symptom in all presentations, as influenza causes a lung infection known as pn. Those with advanced age will often have some confusion, along with a non-focal fever and cough. Anyone coming in with any exacerbation of chronic disease, e.g. lung disease or heart disease, should be screened for influenza during the season, given its association as an illness trigger.

3. How can I protect myself from getting the flu?

• The influenza vaccine
• Hand-washing : think about doing this more often during this time of the year -particularly when you touch a public surface or object (e.g. pen, doorknob). It might be a good time to get used to the fist-bump or bowing or maybe just remembering to use alcohol rub if you shake someone’s hand – and wash your hands before eating.
• Quit smoking :  Smokers have a greater risk of more severe sequellae. It may be a good time to consider quitting or seriously reducing.
• Limit alcohol : For multiple reasons, excessive alcohol intake can affect the immune system and increase the risk of aspiration which is likely a risk factor to secondary bacterial infections in influenza. My recommendation would to limit alcohol to no more than 1 or 2 drinks a day or less.
• Eat a healthy diet, maintain a healthy weight :  Eating a variety of vegetables rife with minerals and vitamins is a great way to bolster the body’s immune system. Various vitamins such as vitamin A, D and to a lesser extent C and E have been shown to affect the immune system in deficiency states. (complexity alert) For instance Vitamin A deficiency was found in mice to impair respiratory epithelium (layer) regeneration and antibody response to influenza A (link). Vitamin D has been touted to be beneficial from a meta-analysis to reduce risk of infection, but there is some conflicting evidence from other studies (link) . Nevertheless there is some biologic plausibility that Vitamin D plays a role in both adaptive (T- and B-cell) and innate (Natural killer, macrophages,etc) immunity (link). A prospective controlled study of 463 students 18 to 30 years old showed a benefit in the use of mega-doses of vitamin C, with a reduction in symptoms and severity (85% reduction) if taken before or after the appearance of cold or flu symptoms. A study on vitamin E in mice showed a reduction in influenza viral titer (amount), possibly linked to enhanced T helper 1 (TH1) cytokines.
• Get plenty of sleep:   I will explore the topic of sleep and immunity on another post. Suffice it to stay, the many effector signals are involved in keeping our immune system robust and sleep is an important piece of the puzzle of why some people get more severe infections than other.
• Exercises and keep a stress-free lifestyle

Obesity has come out as a new risk factor since the 2009 H1N1 pandemic flu season. One study looking at the cases of influenza showed an increase risk of hospitalization for a respiratory illness. In a person with class I obesity (BMI 30-35) the odds ratio was 1.45 and class II (BMI 35-40) and III (BMI 40-45) obesity, the odds ratio was 2.12 — for pneumonia and influenza. This fits similarly the association of more severe presentation of influenza and chronic diseases including diabetes, lung and heart disease and advanced age (impaired immunity).

4. Do omega-3 fish oils help influenza?   NO, I was asked this question recently. From my review online, fish oils may impair immune reactivity from the influenza virus (lower IgG and IgA levels) but may not have clinical impact. In one study in 1999, fish oils had anti-inflammatory properties and led to less viral clearance and some increase symptoms in mice but did not change the outcome. The possiblity of worsening the severity of influenza was suggested in another mice study

At this point, I am going with the likelihood that fish oils do not enhance one’s recovery from influenza.

5.  Are there any treatment options available for influenza?  YES.  Oseltamivir and Baloxavir.  Oseltamivir (Tamiflu) is given twice daily over five days and is a neuraminidase inhibitor, which blocks an important step of viral progeny (new virions) leaving an infected cell to go on to infect other cells.  Baloxavir is a single-dose option recently approved for this flu season (Oct 2018) and has a novel mechanism – a endonuclease inhibitor, which blocks a step needed in viral replication (“making copies”).  The important thing about these medications is that they have to be taken within 24-48 hours of the onset of flu symptoms to experience the maximal benefits, which amount to a reduction of severity and duration by a few days.

Not everyone requires this therapy, particularly in those with mild disease.  I would recommend that anyone with an age over 60 or BMI >30 and/or with conditions such as diabetes, cirrhosis, cardiovascular or pulmonary diseases consider taking this medication to reduce the risk of severity and duration.  Patient with lymphoma and leukemia or solid organ cancer are also at higher risk of complications.  In all of these patients, I would suggest if they present with disease within 24-72 hours or are hospitalized even after this period, that they receive the therapy.

Conclusion

I hope that you have an uneventful flu season – and if you get it this year, I hope it is as mild for you as the common cold. There are things you can do to ensure that it is. Though, remember influenza can be a significant disease. Please refer to my prior blogs on “Respiratory infections” and “10 ways to stay clear from infectious diseases”. Thank you for reading this and please share!