When is Measles Season?

For a while, especially once we eliminated the endemic spread of measles, we weren’t thinking about measles seasons anymore.

In addition to the recent rise in measles cases, this slide shows the patterns of measles seasons in different parts of the world.
In addition to the recent rise in measles cases, this slide shows the patterns of measles seasons in different parts of the world.

Unfortunately, with ongoing outbreaks and rising cases, many people are asking again – just when is measles season?

When is Measles Season?

Traditionally, the time when measles case counts are the highest occurs:

  • during the late winter and early spring (temperate climates, like the United States)
  • after the rainy season (tropical climates)
  • when kids are in school

So just like flu season, it’s always measles season somewhere…

And in areas of the world where measles is still highly endemic, you can expect cycles of larger measles epidemics every 1 to 4 years.

Can you guess why?

“As higher uniform population immunity is achieved the scale of epidemics, both their duration and absolute number of cases, progressively decreases. Epidemic frequency simultaneously decreases with increasing time intervals between epidemics. Another uniform feature as elimination is approached is the loss of epidemic seasonality.”

Durrheim et al on Measles – The epidemiology of elimination

I’ll give you a hint – there is nothing different about the measles virus during those years.

Eventually though, as the number of people susceptible to measles builds up, there is the opportunity for bigger outbreaks. Of course, that doesn’t happen if most people are vaccinated and protected.

When is Measles Season in the United States?

What about in the United States in the post-vaccine era?

Visiting a place with a lot of measles, especially if you aren't vaccinated and protected, increases the risk that you will bring measles home with you and start an outbreak.
Visiting a place with a lot of measles, especially if you aren’t vaccinated and protected, increases the risk that you will bring measles home with you and start an outbreak.

We don’t really have a measles season, as all of our cases are now imported from other parts of the world.

  1. Where and when are folks traveling?
  2. Where is measles on the rise?

That’s when we will see more measles cases here.

“Source countries included Philippines (14 cases), Ukraine (8), Israel (5), Thailand (3), Vietnam (2), Germany (2), and one importation each from Algeria, France, India, Lithuania, Russia, and the United Kingdom.”

Increase in Measles Cases — United States, January 1–April 26, 2019

In the early part of 2019, we saw a lot of cases because unvaccinated travelers were returning from Philippines, Ukraine, and Israel, countries in peak measles season.

Are Europe's measles outbreaks slowing down yet?
Are Europe’s measles outbreaks slowing down yet?

As cases in those countries hopefully slow down over the summer, unfortunately, we might see a rise in other parts of the world.

Of course, there is an easy way to end our measles seasons once and for all.

Two doses of MMR is your best protection against measles.

Get vaccinated and protected, especially before traveling out of the country.

More on Measles Season?

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