Measles diagnosis was confirmed in the patient on July 16 by detection of measles virus by real-time polymerase chain reaction (PCR) from a nasopharyngeal swab specimen collected early on July 15; a positive measles immunoglobulin
M (IgM) antibody titer was reported on July 20.
In our case, both measles immunoglobulin
(Ig)-M and IgG were positive.
The criteria for the laboratory diagnosis included the presence of measles immunoglobulin
(Ig) M, isolation of measles virus, or identification of measles virus by reverse transcription PCR (2,3).
A confirmed case is an acute febrile rash illness with isolation of measles virus from a clinical specimen; or detection of measles-virus specific nucleic acid from a clinical specimen using polymerase chain reaction; or immunoglobulin G seroconversion or a significant rise in measles immunoglobulin
G antibody using an evaluated and validated method; or a positive serologic test for measles immunoglobulin
M antibody; or direct epidemiologic linkage to a case confirmed by one of these methods.
Of the serum samples tested, 1,053 (15%) of 6,999 were positive for measles immunoglobulin
(Ig) M; most were collected during 2006 (Figure 1).
On April 15, 2016, local public health officials in Shelby County, Tennessee, were notified of a positive measles immunoglobulin
M (IgM) test for a male aged 18 months (patient A).
According to JRF data, the number of specimens tested annually for measles immunoglobulin
M (IgM) increased 51% during 2010-2014, from 171,170 to 258,339.
Testing for measles immunoglobulin
G (IgG) and immunoglobulin M (IgM) and testing for measles virus RNA by reverse-transcription polymerase chain reaction (RT-PCR) were performed, and measles genotype was determined.
Serum collected on April 5 was positive for measles immunoglobulin
A serum specimen collected on January 31 demonstrated a high titer of measles immunoglobulin
M (IgM) and was positive for measles immunoglobulin
G (IgG) on testing at a reference laboratory.
Laboratory confirmation of measles is made by detection in serum of measles-specific immunoglobulin M (IgM), a significant rise in measles immunoglobulin
G (IgG) level, isolation of measles virus, or detection of measles virus by nucleic acid amplification from a clinical specimen.
All three specimens subsequently were forwarded to CDC for serologic confirmation and virologic testing; serology performed on March 30 was measles immunoglobulin
M (IgM)-positive, indicating acute infection.