Respiratory syncytial virus (RSV) season

It's influenza-like illness ("ILI") season again. We just call it flu season but in fact there are a lot of respiratory viruses running around besides the flu virus that look like flu. Recently we discussed one of the others, the human metapneumovirus (HMNV). It's been around infecting us for over a century but wasn't identified until 2001. One we've known about a little longer (1956) is respiratory syncytial virus (RSV), a major cause of respiratory infections in children and increasingly in adults, especially the elderly. Like influenza and HMNV, RSV is a negative sense single stranded RNA virus with an envelope. That means its genetic material is RNA instead of the DNA we have as the carrier of our genetic information. The negative sense part means that it makes protein via an RNA intermediate rather than directly. There are only two known strains (A and B) and there is no post infection immunity. You can get it again the next season. It's in the same family as measles and mumps virus (Paramyxoviridae).

RSV is mainly a "common cold" virus but in infants and children it goes down into the lungs to cause "bronchiolitis." This sounds like a pathologic diagnosis (inflammation of the small airways called bronchioles), and it is, but this is primarily a clinical diagnosis: cough, fever, shortness of breath, wheezing. It's one of the most common causes of pneumonia in children and is a costly illness, overall, with 75,000 to 125,000 hospitalizations of kids under 1 year old each year. If October to March is "flu season," what is "RSV season"?That's harder to say, and interestingly, it seems to circulate at different times in different communities. We don't know why, although environmental factors like temperature and humidity probably play some part. Timing seems to vary in different years, as well. CDC's Morbidity and Mortality Weekly Reports (MMWR) just did a brief report on the timing of RSV in 2007 - 2008. This chart shows onset and termination of RSV outbreaks in the 10 Health and Human Services regions. It looks like flu except for the Florida region, where things started in July. Notice that different regions started at different times as well (Source: MMWR).


This year Florida is again the outlier (onset in July). Here's how it's shaping up so far this year, in the US:

Reports received through December 6, 2008, indicated that the RSV season onset had begun in mid-October in Region 4 (Atlanta) (excluding Florida [week ending October 11, 2008]) and in late October in Region 6 (Dallas) (week ending October 25, 2008). The season had begun in Region 1 (Boston) and Region 2 (New York) in mid-November (week ending November 15, 2008), followed by Region 3 (Philadelphia) (week ending November 22, 2008), and Region 9 (San Francisco) and Region 10 (Seattle) (week ending November 29, 2008). The Region 5 (Chicago) season onset occurred in early December (week ending December 6, 2008). As of December 6, 2008, the RSV season onset had not started in Region 7 (Kansas City) and Region 8 (Denver). In Florida, reports indicate that the season onset occurred in mid-July (week ending July 12, 2008), 1 week later than in 2007. Nationally, the 2008--09 RSV season onset occurred the week ending November 1, 2008; however, when data from Florida are excluded, the national season onset occurred 2 weeks later (week ending November 15, 2008). (MMWR, CDC)

If you want to keep score as the season progresses, you can to to CDC's National Respiratory and Enteric Virus Surveillance System (NREVSS) website for weekly updates.

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One problem for the clinician (and state DPH) is that there are readily available office rapid tests for RSV and influenza, but not for metapneumovirus, coronavirus, rhinovirus and others. It become hard to track which ILI is making your patient sick unless you have research access to testing (viral cultures take too long to be practical.)

Another problem for the clinician is insurance companies dictating when you can use anti-RSV drugs in premies based on their opinion of when the season runs... which is variable from year to year.

A third problem is over-treatment of RSV with antibiotics and steroids (the only thing that works is oxygen, fluids and time.)

In a nutshell, if you want to look at controlling costs, it ain't as easy as it looks on TV.

Caught RV last year from my grandson, an early holiday gift. If I had adequate sick time, I would have taken off about four weeks to recuperate, because from Thanksgiving to mid-January, all I did was cough my eyeballs out. Thought I'd broken a few ribs or had 'the grippe'.

Poor kids who get this...

Agree 100% with Dem re: cost management. People are not widgets (with predictable production and repair times), even if they are fortunate enough to have adequate health care AND prescription coverage.

In my opinion the largest threat for California are cataclysms and ecological catastrophes. Not important is how many money we have because one tragedy can us take all.

Is there any evidence that some regions of the country see significantly more ILI than others? Since they seem to be predominantly in the winter here in PA, I'd expect that perhaps an area like southern California might see a lot less ILI.