The Centers for Disease Control and Prevention (CDC) cautioned that while in the United States, cases of mpox (formerly known as monkeypox) have declined since the peak in August 2022, the outbreak is not over.

In a May 15 Health Alert, the CDC said it continued to receive reports of cases that reflect ongoing community transmission in the United States and internationally. Currently, the CDC and local partners are investigating a cluster of mpox cases in the Chicago area. From April 17 to May 5, 2023, a total of 12 confirmed and one probable case of mpox were reported to the Chicago Department of Public Health. All cases were among symptomatic men. None of the patients have been hospitalized, according to the CDC.

Nine of the 13 cases were among men who had received two JYNNEOS vaccine doses. Travel history was available for nine cases: four had recently traveled (New York City, New Orleans and Mexico).

The CDC noted that although vaccine-induced immunity is not complete, vaccination continues to be one of the most important prevention measures. The agency expects new cases among previously vaccinated people to occur, but people who have completed their two-dose JYNNEOS vaccine series may experience less severe symptoms than those who have not.

Although approximately 1.2 million JYNNEOS mpox vaccine doses have been administered in the United States since the beginning of the outbreak, only 23% of the estimated population at risk for mpox has been fully vaccinated. To help prevent a renewed outbreak during the spring and summer months, the CDC is urging clinicians to be on alert for new cases of mpox and to encourage vaccination for people at risk. If mpox is suspected, test even if the patient was previously vaccinated or had mpox. Clinicians should also refamiliarize themselves with symptoms, specimen collection, laboratory testing procedures and treatment options.

For specimen collection, the CDC says that all recommended PPE should be worn when collecting a specimen from a person with suspected or confirmed mpox. Only sterile, synthetic swabs with plastic, wood or thin aluminum shafts should be used to collect suspected or confirmed mpox specimens for diagnostic testing. Do not use cotton swabs. More information on handling of specimens and testing procedures is available here.