influenza treatment – Doctor Rennie's Blog

Influenza causes major illness every year despite vaccines and treatment options. The 2024-2025 season was a busy one. By mid-January 2025, the CDC had reported over 10 million flu-related illnesses and about 120,000 hospitalizations, numbers that ran ahead of the prior year. Flu season typically peaks between December and February. That swing from year to year reminds us how much flu activity depends on strain changes, how many people get vaccinated, and what immunity looks like across the population.

Why History Matters

Flu is not new. The 1918-1919 pandemic killed an estimated 50 million people worldwide. Three later pandemics, in 1957, 1968, and 2009, each showed how dangerous a new strain can be. Every one of them pushed public health toward stronger vaccines, better antivirals, and better surveillance.

Public Health Impact

Every year influenza causes between 290,000 and 650,000 deaths worldwide. Young children, older adults, pregnant people, and those with chronic conditions carry the most risk. Flu season also strains hospitals and clinics, and it costs billions in missed workdays and healthcare spending on top of the direct health toll.

How Flu Spreads

The incubation period is short, usually about two days. Transmission happens through droplets, when people cough, sneeze, or talk, and through contaminated surfaces if someone touches their face afterward. In households and schools, attack rates can reach 20 to 30 percent.

People can spread flu a full day before symptoms start, and for up to a week after. Immunocompromised patients can spread it longer than that.

Symptoms and Complications

Classic symptoms are fever, cough, sore throat, body aches, fatigue, and headache. Children are more likely than adults to get vomiting or diarrhea along with it.

For most people the illness runs its course. But complications are common enough to take seriously: secondary bacterial pneumonia, worsening asthma or COPD, myocarditis, encephalitis, even ARDS. These are the cases that fill hospital beds every winter.

Influenza A and B

Both influenza A and B drive seasonal flu, but they behave differently. Influenza A is more common, infects humans and animals, and is behind pandemics. Subtypes like H1N1 and H3N2 are defined by their surface proteins. Influenza B only infects humans, and it has two main lineages, Victoria and Yamagata. Outbreaks from influenza B tend to be smaller but still cause serious illness, especially in children. A often dominates earlier in the season, while B shows up later, though they can circulate together.

Diagnosis

Most of the time, diagnosis starts clinically. But testing can confirm it. Rapid tests give results in about 15 minutes, though sensitivity is limited. RT-PCR is much more accurate and is considered the gold standard.

Vaccination

The flu vaccine changes yearly to match expected strains. For 2024-2025, the U.S. vaccine was trivalent, not quadrivalent: two influenza A strains, H1N1 and H3N2, and one influenza B strain, Victoria. B/Yamagata was left out of that season’s formulation, per the CDC’s ACIP recommendations, because global surveillance had not detected it since 2020.

Effectiveness runs 40 to 60 percent, depending on the match and the patient’s age and health. Vaccines come in several forms: inactivated injectable, live attenuated nasal spray, and higher-dose or adjuvanted versions for older adults.

Treatment

Antivirals work best started within 48 hours of symptoms. Oseltamivir is oral and the one used most. Zanamivir is inhaled, peramivir is intravenous and usually reserved for hospitalized patients, and baloxavir is a single-dose oral option that blocks replication.

Supportive care still matters most: rest, fluids, acetaminophen or ibuprofen for fever and pain, and close monitoring for complications in anyone at higher risk.

Prevention

Annual vaccination is the best prevention. Handwashing, covering coughs, staying home when sick, and avoiding close contact with ill people all reduce spread. Masks and improved ventilation are useful in crowded settings, especially when flu activity runs high.

Final Notes

Flu is not going away. Each season differs, but the tools we have (vaccines, antivirals, good hygiene, early recognition) make a real difference when used consistently. As physicians, we need to push vaccination, treat high-risk patients early, and keep reminding our communities that influenza is more than “just a cold.”

—

Scott Rennie, D.O.
Board Certified in Obesity Medicine and Family Medicine

This blog is for educational purposes only and does not constitute individual medical advice. Always consult your own physician before making changes to your health, medications, or treatment plan.

Sources

Centers for Disease Control and Prevention. FluView Surveillance. https://www.cdc.gov/fluview/surveillance/index.html
World Health Organization. Influenza (Seasonal). https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal))
Dawood FS, et al. Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modelling study. Lancet Infect Dis. 2012;12(9):687-695. PMID 22738893.
Grohskopf LA, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2024-25 Influenza Season. MMWR Recomm Rep. 2024;73(RR-5):1-25. PMID 39197095.

I’ve seen quite a few patients this year who have tested positive for influenza. Many people have questions about whether they should get the flu shot, or how to treat the infection. Influenza is also called the flu, and is highly contagious. It occurs in both children and adults. It is more common in the winter during “Flu Season” which is generally from about November through March but in 2012 we have seen many flu cases in April. Spread: Flu is spread from person to person by coughing, sneezing or touching things that an infected person has previously touched. More than 200,000 people are hospitalized each year in the United States due to influenza. Serious illness is more likely in the very young and in older adults, pregnant women or individuals who have chronic medical problems. Symptoms: These vary from person to person but some common characteristics are: 1) Temperature higher than 100 degrees F 2) Fatigue 3) Cough and sore throat 4) Headache and/or muscle aches The fever usually lasts from 2-5 days. In most other respiratory infections that cause fever, the fever resolves within 24-48 hours. Most people who get the flu feel worse than when they have a common cold although the symptoms can be similar. Usually the fever and aches/chills are the symptoms that cause the most discomfort. Complications of flu: Pneumonia is the most common complication. This is a serious infection of the lungs as is more likely in people over age 65 or individuals who live in long term care facilities (nursing homes) or those with other illnesses such as diabetes or chronic lung or heart problems. Diagnosis: We can usually diagnose the influenza in the office by a special Q-tip (swab) that it inserted into the nose and then tests for influenza virus. Treatment: Influenza is a virus and the body is able to fight off the virus even without medications in the majority of cases. The symptoms can be miserable however and many patients are given medications for fever, sore throat, cough or nausea. Sometimes antiviral medications such as Tamiflu, Relenza, Flumadine or Amantadine can be effective, but this medicine is not very helpful if the symptoms have been present for more than 48 hours. Antibiotics are not useful for treating influenza because they only work against bacteria. H1N1 (Swine flu): A new strain of H1N1 influenza that contains parts of swine, avian and human influenza viruses was first noted in humans in March of 2009 in Mexico. There were human infections noted around the world until August 2010 and the symptoms of the Swine H1N1 flu virus and treatment for it were generally similar to those of seasonal flu. Avian (Bird flu): A strain of influenza virus that originally infected birds such as chickens, ducks and geese has spread to humans and caused several deaths to date, mostly in Asia. Avian flu has mostly been spread from bird-to-bird and much less from bird-to-human. Human-to-Human transmission of the bird flu has only rarely occurred. Most people who have been infected with bird flu have had direct contact with sick or dead birds or recently visited a live poultry market. No human cases of avian influenza have been found in the US or anywhere else in North America to date. A great resource for more information on influenza, and about up to date flu activity and surveillance is the Centers for Disease Control: http://www.cdc.gov/flu/index.htm I hope that you have found this information useful. Wishing you the best of health,