Thread by @ClementLeeMD

With RSV season now formally upon us, let’s learn a little bit about the virus! Here are 10 facts you may not know about RSV…

#PedsTwitter #MedTwitter

1. RSV is the #1 cause of hospitalizations in children under age 1 in the US (PMID 27490190).

(Technically, by billing codes, this is inaccurate—since being born is the #1 cause of hospitalization, but you get the idea.) 👩‍🍼

2. Worldwide, the #1 killer of infants after the neonatal period is malaria. 🦟🩸

#2 is RSV (PMID 23245604).

RSV accounts for 7% of infant deaths (and malaria 12%).

3. In the US, RSV actually kills more ADULTS than children every year. 🧓

Per the CDC, RSV kills 14,000 adults and 100-500 kids every year.

ndc.services.cdc.gov/case-definitio…

Which animal was RSV originally isolated from? 🐕🐔🐒🐷

4. RSV was originally called the chimpanzee coryza virus because it was isolated from a chimp (PMID 2046710).🐵

As expected from the name (coryza means runny nose), one of the hallmarks of infection is rhinorrhea.

5. RSV (respiratory syncytial virus) gets its name from its F protein causing epithelial cells to fuse together and form giant cells called “syncytia.”

Syncytia are prone to necrosis, sloughing into the airways and plugging them up. This leads to respiratory distress. 🤧

The F protein is the target of some monoclonal antibodies meant to prevent disease, including palivizumab and nirsevimab. I write more about this in @NEJMRes360:

resident360.nejm.org/from-pages-to-…

6. RSV is usually more prominent in the winter in the US. However, Hawaii and Florida have RSV year-round (!!!) 🏝️🍹

(PMID 17639745, PMID 1774271)

I must pour one out for my fellow pediatricians in Florida and Hawaii who have to deal with this all year. 🍻

7. Younger kids with RSV have more crackles and apnea. Older kids have more wheezing (PMID 35785792). 🫁

8. In the classic trial that led to Synagis approval, there actually was NO benefit in patients with cyanotic CHD, and the positive primary outcome was driven by benefit in those with acyanotic CHD (PMID 14571236). ❤️‍🩹

No explanation was posited and I can’t think of a plausible mechanism either. 🤔

There was a prior signal of patients with cyanotic CHD having more surgical complications after Synagis, but surgical outcomes were same in this study (though not stratified by type of CHD)...

9. It’s commonly taught that RSV severity peaks on days 3-5. I’ve found this “pearl” lacking hard evidence and not useful clinically.

If a child looks good on day 2, I would d/c home. If a child looks awful on day 6, I would admit or escalate care.

https://twitter.com/ClementLeeMD/status/1519094887651684352?s=20&t=bDPuCYR7mg1g9PF9zHa6Hg

10. October is RSV awareness month. Let’s continue educating each other about it! 🎗️

#RSVawareness

aarc.org/an21-october-i…

We don’t have great treatments, and some even lead to WORSE outcomes, like deep suctioning. 🪠

As such, prevention is key. Please, wash your hands and don’t kiss babies. Also, HCWs—please don’t work if you are sick. A “cold” for you may end up taking the life of another. 🤒

#PedsTwitter, anything else to add? @Kind4Kids @DrEricBall @DrClaire @DoctorNatasha @WendySueSwanson @MichaelCosimini

Also see @drkatielockwood's wonderful thread that inspired this one:

https://twitter.com/drkatielockwood/status/1583529664467066881?s=20&t=bDPuCYR7mg1g9PF9zHa6Hg