Flu, RSV, or COVID-19? Convergence of Three Viruses Creates Risk of Diagnostic Errors

Healthcare practitioners will encounter flu, RSV, and COVID-19 year-round, with peaks in fall and winter that can strain clinics and hospitals. These surges may overwhelm primary care offices and emergency departments, creating shortages of pediatric and adult hospital beds. To promote and improve patient safety, office practices should prepare now to vaccinate and test for flu, RSV, and COVID-19.

Vaccination

For the 2025–2026 season, vaccines are available for all three viruses.

Flu vaccines: This year’s updated trivalent formulations protect against (A)H1N1, (A)H3N2, and B/Victoria lineage-like virus. See CDC Updates for the 2025–2026 Flu Season and Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP)—United States, 2025-26 Influenza Season.

RSV vaccines: There are revisions in last year’s CDC recommendations.

• Adults: According to the CDC’s RSV Vaccine Guidance for Adults: “The RSV vaccine is not currently an annual vaccine, meaning eligible adults do not need to get a dose every RSV season.” Current recommendations include only a single dose for adults ages 75 and older and for patients at increased risk of severe RSV, ages 50 to 74. For RSV, currently there are three vaccines available for adults: GSK's Arexvy (age 50 or older), Moderna's mResvia (age 60 or older), and Pfizer's Abrysvo (age 18 or older and pregnant women completing 32 to 36 weeks).
• Pregnant individuals: The CDC recommends a single dose of the maternal RSV vaccine at 32 to 36 weeks of gestation (to protect infants up to 6 months old), ideally administered between September and January. See the CDC RSV recommendations for pregnancy, also stating: “Pfizer’s Abrysvo is the only RSV vaccine recommended for pregnant women. GSK’s Arexvy and Moderna’s mResvia are not approved for use during pregnancy.”
• Infants: The CDC recommends the infant RSV antibody “for infants younger than 8 months of age who are born during or are entering their first RSV season (typically fall through spring)” and meeting certain eligibility criteria. See RSV Immunization Guidance for Infants and Young Children and review information for Beyfortus (a monoclonal antibody, not a vaccine). The American Medical Association provides the resource “RSV Vaccines: Questions Patients May Have and How to Answer.”

COVID-19 vaccines:

• Variants: In August 2025, the FDA updated COVID-19 vaccines to target the LP.8.1 strain and the JN.1 Omicron subvariant, which is closely related to the prevalent XFG (Stratus) variant, with continued emphasis on boosters for high-risk populations. (See the CDC’s Variants and Genomic Surveillance for the latest variant guidance.)
• Informed consent: On October 6, 2025, the CDC adopted individual-based decision-making for COVID-19 vaccines, with recommendations for the provision of informed consent discussions. In addition, some local pharmacies in some states now require a prescription for COVID-19 vaccine administration. See the CDC 2025–2026 COVID-19 Vaccination Guidance and the American Academy of Pediatrics COVID-19 Vaccine Frequently Asked Questions.

Diagnosis

For patients manifesting illness, the challenge in diagnosis is that all three viruses have similar symptoms, and testing must be performed for each to effectively confirm a correct diagnosis. Understanding the differences between the flu, RSV, and COVID-19 will help prevent misdiagnosis or delayed diagnosis when patients present with respiratory symptoms.

The American Academy of Pediatrics and the National Foundation for Infectious Diseases offer information on differential diagnosis between the three viruses. The CDC provides specific guidance on distinguishing the flu and COVID-19. General information for practitioners about each virus is available from the CDC as follows: flu, RSV, and COVID-19. The CDC addresses signs and symptoms, incubation periods, how the viruses spread, individuals at higher risk for severe illness, potential complications, and approved treatments.

Prevention

During flu season, it is possible that all three of the viruses may spread at the same time, and patients could become infected with one or all three of the diseases. To offset this possibility, it is important to offer appropriate screening, testing, and vaccinations. Refer to the CDC’s guidance on the 2025–2026 Flu Season. According to the CDC, “flu, RSV, and COVID vaccines may be given on the same day” if patients are eligible and vaccines follow the appropriate administration schedule. 

Patient Safety Strategies

Enhance patient safety by taking the following actions:

Patient Care

• Follow testing guidelines. Testing is the best method for determining which virus the patient may have while guiding your decisions about the appropriate treatment. Review the CDC’s information for clinicians on influenza virus testing for patients with acute respiratory illness symptoms.
• Encourage your patients to get appropriate age-related vaccines.
• Educate staff and patients on all vaccines.
• Ensure that the patient’s health record includes standard documentation about the possibility of contracting the flu, RSV, and/or COVID-19, including vaccination informed consent and informed refusal discussions. Find a sample informed refusal form on our Informed Consent Sample Forms page.
• Use a shared decision-making approach when discussing vaccination with patients. Clearly explain the potential risks and benefits of being vaccinated versus not being vaccinated. For guidance, refer to the Agency for Healthcare Research and Quality’s resource “The SHARE Approach.”
• Ensure that the shared decision-making and consent discussion is thoroughly documented in the patient’s medical record. For additional information, see The Doctors Company article “Reduce Patient Safety Risks With Vaccinations.”
• Prescribe antivirals as necessary to prevent complications. See the CDC’s “Treating Flu with Antiviral Drugs” and “Types of COVID-19 Treatment” and Medscape’s “Respiratory Syncytial Virus Infection Medication.”
• For patients who experience side effects from vaccines, report issues to the Vaccine Adverse Event Reporting System (VAERS) through the VAERS website, or by calling (800) 822-7967.

Additional Office Measures

Follow these steps to promote patient safety within the office setting:

Infection Control Protocols

• Maintain, update, and document all changes in office policies related to personal protective equipment and infection control. Provide and document staff education on current CDC recommendations for prevention and vaccination.
• Follow CDC guidance:
• Infection Control Guidance: SARS-CoV-2
• Guide to Infection Prevention in the Outpatient Setting
• Ensure all vaccines stored in the office are current and maintained per manufacturer instructions.
• Consider masking for patients, visitors, and staff based on community infection rates and patient population.
• Practice good handwashing.

Vaccination of Staff

• Encourage all staff to receive flu, RSV, and COVID-19 vaccines per current guidelines.
• Offer vaccines at no cost to employees to increase compliance.

Patient Education

• Provide vaccine information sheets and consent forms for each vaccine.
• Print resources and display infographics in your office for the flu, RSV, and COVID-19. Many free resources are available on the web.
• Offer videos in your waiting area to educate patients about infection control and getting vaccinated. Many options are available on YouTube.
• Educate patients to stop the spread of germs:
• Wash hands frequently.
• Maintain respiratory etiquette (including masking when necessary).
• Avoid touching eyes, nose, and mouth.
• Avoid close contact, particularly with those who are sick.
• Disinfect frequently contacted surfaces and objects.
• Encourage self-isolation if sick.

Community Monitoring

• Adhere to local government or public health department recommendations for additional precautions.
• Check transmission levels in your community: “Weekly U.S. Influenza Surveillance Report,” “Surveillance of RSV,” and “COVID Data Tracker.”

For additional assistance, contact the Department of Patient Safety and Risk Management at (800) 421-2368 or by email.