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Testing for respiratory illness

Published January 26th, 2023

Many people have experienced colds or flu-like illnesses already this winter. Experts are monitoring the levels and continued spread of these viruses, including flu, COVID-19, and RSV. This article will answer common questions about testing, treatment, and prevention.

What is the current state of flu, Covid-19, and RSV in the US?

According to the CDC, as of the week of January 14, 2023:

  • Flu is circulating at moderate to high levels, as expected this time of the year, but is continuing to decline1
  • COVID-19 cases and hospitalizations are beginning to decline2
  • RSV is trending down in most areas across the US3

how can I tell which virus I have if I get Flu-like symptoms?

The only way to know which virus you have is to get tested. While at-home tests for COVID-19 are readily available, there are no rapid, at-home tests for flu or RSV. A physician’s office or urgent care clinic can perform a single test for flu, RSV, and COVID-19.

Why is it important to get tested?

Some flu and COVID-19 treatments must be taken within a certain time frame after your symptoms start to be effective. So, the sooner you find out which virus you have, the more options you will have.

For example, Tamiflu, an antiviral medication that targets the flu, is most effective if taken in the first 48-72 hours after symptoms begin.4 Tamiflu can help reduce the severity and duration of flu symptoms and is available by prescription.

Similarly, Paxlovid, the antiviral used to treat COVID-19, works best when taken within 5 days of testing positive.5 Paxlovid can reduce the severity and duration of COVID-19 symptoms (and early data suggest it also reduces the risk of developing long COVID6) and is available by prescription. However, it is important to note that Paxlovid should not be taken by individuals who must take other medications that are also processed by the body through the liver (such as most “statin” based cholesterol medications, among others).  Your physician or pharmacist will guide you about this.

Is it too late to get a flu vaccine?

No, it is not too late to get a flu vaccine. While the ideal time to get a flu vaccine is from mid-September to October, the flu virus typically still circulates at high levels in January and into February, so getting vaccinated now can still provide some protection. Although the flu peaks in the winter in the US, it circulates globally from April to September. If you plan to travel, getting the flu vaccine now can help protect you.

Should I get a bivalent COVID-19 booster?

Bivalent COVID-19 boosters have been shown to greatly protect against severe disease and hospitalization, particularly in patients over the age of 65. Early studies suggest that it offers protection against the latest variants. In fact, a bivalent booster decreases the chance of hospitalization from COVID-19 by 57%7. Despite this, only 17% of adults in the US have had their bivalent booster.2 With cases and hospitalizations still high, getting the bivalent booster is strongly recommended. If you have recently had COVID-19, you can still get a bivalent booster after your symptoms are gone. Given that you will have some immunity after your infection, you may wait to get boosted until 90 days after your infection began. If you are immunocompromised, you may choose to get boosted sooner. (Note: The new bivalent vaccines provide protection against both the original strain and the new Omicron BA. 4/BA. 5 variants. This provides broader protection against COVID-19.)

Will I need to continue to get covid-19 vaccines?

The FDA is currently in the process of determining the best COVID-19 vaccination strategy for continued protection from the virus. The agency recently proposed an approach that involves a single dose of COVID-19 vaccine for healthy adults, and two vaccines per year for young children and high-risk groups8. Annual COVID-19 vaccines would be routinely selected to target specific variants, similar to the way flu vaccines are updated annually.


  1. CDC. Weekly U.S. Influenza Surveillance Report. Centers for Disease Control and Prevention (2022).
  2. CDC. COVID Data Tracker. Centers for Disease Control and Prevention (2020).
  3. RSV National Trends – NREVSS | CDC. (2023).
  4. TAMIFLU® (oseltamivir phosphate).
  5. PAXLOVIDTM (nirmatrelvir tablets; ritonavir tablets) For HCPs.
  6. Nirmatrelvir and the Risk of Post-Acute Sequelae of COVID-19 | medRxiv.
  7. Tenforde, M. W. Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–Associated Emergency Department or Urgent Care Encounters and Hospitalizations Among Immunocompetent Adults — VISION Network, Nine States, September–November 2022. MMWR Morb Mortal Wkly Rep 71, (2022).
  8. Reuters. U.S. FDA proposes shift to annual COVID vaccine shots. Reuters (2023).