AFM Cases and Outbreaks

As of September 30, 2020, there have been 22 confirmed cases in 2020. There are 49 reports of patients under investigation (PUIs) for 2020. Two patients with confirmed AFM died in the acute phase of their illness, one in 2017 and one in 2020. We have also learned of deaths in cases confirmed in previous years.

There were 46 confirmed cases in 2019 out of 142 PUIs. CDC, state, and local health departments are still investigating some of the PUIs.

There have been 639 confirmed cases since CDC began tracking AFM in August of 2014. CDC has been thoroughly investigating cases since that time. We have seen increases in AFM cases, mostly in young children, every two years.

Annual AFM Cases by State

Annual maps represent only cases for whom information was sent to and confirmed by CDC as of September 30, 2020. Patients under investigation are still being classified, and the case counts are subject to change. Cases of AFM have occurred in 49 states and the District of Columbia.

AFM Reported Cases 2020

Thus far in 2020, there have been 22 confirmed cases in 13 states and the District of Columbia.

We defer to the states to release additional information on cases as they choose.

Cases by Month, 2014-2020

Most patients had onset of AFM between August and November, with increases in AFM cases every two years since 2014. Many viruses commonly circulate at this same time of year, including enteroviruses, which are likely responsible for the increase in cases in peak years.

Confirmed AFM cases by CDC

Confirmed AFM cases reported to CDC: Aug-14=21, Sep-14=51, Oct-14=24, Nov-14=15, Dec-14=9, Jan-15=2, Feb-15=2, Mar-15=1, Apr-15=0, May-15=1,  Jun-15=0, Jul-15=2, Aug-15=3, Sep-15=1, Oct-15=4, Nov-15=2, Dec-15=4, Jan-16=1, Feb-16=0, Mar-16=6, Apr-16=1, May-16=7, Jun-16=9, Jul-16=13, Aug-16=33, Sep-16=43, Oct-16=27, Nov-16=9, Dec-16=4, Jan-17=2, Feb-17=5, Mar-17=5, Apr-17=4, May-17=2, Jun-17=4, Jul-17=3, Aug-17=1, Sep-17=4, Oct-17=0, Nov-17=3, Dec-17=5,  Jan-18=0, Feb-18=4, Mar-18=1, Apr-18=2, May-18=3, Jun-18=8, Jul-18=8, Aug-18=30, Sep-18=88, Oct-18=66, Nov-18=21, Dec-18=7, Jan-19=2, Feb-19=4, Mar-19=4, Apr-19=3, May-19=5, Jun-19=2, Jul-19=5, Aug-19=4, Sep-19=6, Oct-19=7, Nov-19=2, Dec-19=2, Jan-20=7, Feb-20=2, Mar-20=3, Apr-20=1

^ Confirmed AFM cases by CDC from August 2014 through September 30, 2020. Case counts are subject to change.

* The data shown from August 2014 to July 2015 are based on the AFM investigation case definition: onset of acute limb weakness on or after August 1, 2014, and a magnetic resonance image (MRI) showing a spinal cord lesion largely restricted to gray matter in a patient age ≤21 years.

† The data shown from August 2015 to present are based on the AFM case definition adopted by the Council of State and Territorial Epidemiologists (CSTE): acute onset of focal or flaccid limb weakness and an MRI showing spinal cord lesion largely restricted to gray matter and spanning one or more spinal segments, regardless of age.

For more information, visit the Case Definitions page.

It is currently difficult to interpret trends of the AFM data. Collecting information about PUIs for AFM is relatively new. There may initially be more variability in the AFM data from year to year, making it difficult to interpret or compare case counts between years.

Page last reviewed: October 2, 2020