Summary: The 2019-2020 influenza season is off to an early start. Interestingly, the majority of cases have been associated with influenza B. With an increase in influenza-like illness identified in these last few weeks, it is possible that this season could be similar or worse than the 2017-2018 season. Brace yourselves for an active season.
Welcome to the new year 2020. As expected, at around the 46-48 week of 2019, we exceed the baseline of 2.5% of influenza-like illness (ILI). The percentage of ILI has soared in the last few weeks compared to what it was last season. Presently in United States, the seasonal influenza epidemic is widespread. This season has been unique from others in the percentage of cases attributable to influenza B followed by H1N1. The Centers of Disease Control (CDC) estimates approximately 64% of the flu cases are from influenza B. Usually, influenza B cases pick up towards the second half of the season.
From the FLUVIEW CDC site (above), there has been a very high level of influenza-like activity. Influenza has a high attack rate, affecting 5-10% of the adult population and 20-30% of the population of children. High ILI activity suggests that there will be a high rate of transmission in those affected areas.
The current activity in this flu season is already trending toward a higher caseload than 2017, with a steeper and earlier curve than in 2017-2018 (see red line in the graph below). That season was the most severe season in recent years. By April 2018, more than 34 million people had the flu, about 1 million were hospitalized, and approximately 54,000 people died. These deaths are usually from a secondary bacterial infection, complications of respiratory distress, or a cardiovascular complication attributable to influenza. Although we have yet to see the peak of this season, should the percentage of ILI exceed those of 2017-2018, it is possible that this season will see a record number of influenza-attributable hospitalizations and deaths.
The curve has come down from its peak at about week 52. It is not clear yet and it is still fairly early in the season for the possibility of another increase. What also is important to mention is that the rate of laboratory-confirmed influenza hospitalizations is less than where cases were for 2017-18 at the similar time. Though, it is still too early to tell.
The good news is that if you have received the vaccine, you are likely to either be protected from the disease or get a milder case. The CDC estimates the average efficacy of influenza vaccination ranges from 40 and 60%. Other than getting a milder infection, the vaccine reduced the risk of the influenza-associated diseases, such as heart failure, respiratory failure, and secondary pneumonia. Predictions for the 2019-2020 influenza vaccination are forthcoming. The components for the H1N1 vaccine and usually for influenza B are more effective than the H3N2 (H1N1 (75-80%), H3N2 (20-25%)). Last season, the estimated vaccine efficacy was 47%, approximating 61% in ages 7 months to 18 years, and lower in the over 50 age group.
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.
The vaccinations consist of two type of influenza viruses, influenza A and B. Type A viruses are named after cell membrane (the outer layer of a virus) components – called hemagglutinin (H) and neuraminidase (N). The 2019-2020 vaccines are quadrivalent, consisting of 2 types of A viruses (H1N1 pandemic 2009 and H3N2) and 2 The type B viruses named after lineages B/Yamagata and B/Victoria. The influenza B cases for 2019-2020 are from the B/Victoria lineage.
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:
- 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.
- 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. How does this happen? 1) the droplets can land on a surface and you can touch it and then put your fingers in your mouth or touch food you then eat; 2) Person-to-person a person could cover their cough and sneeze and shake your hands 3) 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 common cold (rhinovirus), the symptoms for the flu come on abruptly. There will be fatigue and muscle aches, though cough is the most common symptom. The reason is that influenza causes varying degrees of infection in the lungs, known as pneumonitis. Those with advanced age may have confusion or delirium along with a non-focal fever and cough. Anyone coming in with any exacerbation of chronic disease, e.g. lung disease or heart disease or even a heart attack, should be screened for seasonal influenza, given its association as an illness trigger.
3. How can I protect myself from getting the flu?
- The influenza vaccine – Get it sooner than later.
- 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 do the fist-bump, air handshake, 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. 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. 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. 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. 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. It likely reduces the severity and shortens the course by a few days. Take the therapy within a day of onset.
- Baloxavir is a single-dose option recently approved for this flu season (Oct 2018) and has a novel mechanism – an 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 treatment other than supportive care, 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. Happy New Year 2020! I hope that you have an uneventful 2019-2020 flu season. If you are unfortunate to 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. Remember influenza can be a significant disease. Thank you for reading this post and please share this to your friends and contacts. If you want to stay up-to-date with future Your Health Forum posts, register your email on the the side panel.
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Categories: Infectious Diseases Topics