Clade I Mpox: US Cases Update, Connecticut Confirms First

Overview

Connecticut’s Department of Public Health confirmed the state’s first Clade I mpox infection in a person recently returned from Western Europe. Officials emphasize the low risk to the general public while urging those at higher risk to complete the two-dose JYNNEOS vaccine series to reduce illness and transmission risk.

What is Clade I Mpox?

Clade I is one of the primary genetic groups of the mpox virus and has long circulated in Central and Eastern Africa where it has produced more severe disease and higher fatality rates in vulnerable populations. Symptoms typically begin 7–21 days after exposure and include fever, headache, swollen lymph nodes, and a rash that can appear on the body or genitals. Severe complications can include bacterial superinfection, encephalitis, or pulmonary involvement.

For clinical guidance, see the CDC clinical overview.

U.S. cases and the Connecticut mpox case

The Centers for Disease Control and Prevention reports 11 Clade I mpox cases in the United States from November 2024 through February 2026. Many cases have been travel-associated or linked to small domestic clusters identified by genomic analysis. The first confirmed U.S. Clade I case was travel-related in California.

Connecticut public health officials reiterated there is no evidence of sustained community transmission but advised people at risk to get vaccinated. CT DPH Commissioner Dr. Manisha Juthani said:

“Mpox hasn’t gone away, and we want people to be protected, especially as many in our community prepare for travel, festivals, and gatherings this summer. The vaccine is safe, effective and widely available. Completing the two-dose series is the best way to protect yourself and your partners.”

For the CDC’s situational context, see the CDC Situation Summary and the CDC media notice about the first U.S. Clade I case in California at the CDC media release on first U.S. Clade I case (California).

Global outlook and the emerging Clade Ib

Clade I activity remains concentrated in parts of Africa, where 2024 reporting included tens of thousands of suspected cases and over a thousand deaths in the Democratic Republic of the Congo and across the region. These outbreaks reflect the higher disease burden Clade I can cause, especially where access to timely care is limited.

Researchers are monitoring a subclade referred to as Clade Ib, noted for household spread, higher apparent mutation rates, and some sexual transmission clusters. These shifts could affect outbreak dynamics and diagnostic sensitivity; PCR testing remains the primary diagnostic tool but may be challenged by some variants. See analysis at PMC review of Clade Ib and recent research and the Johns Hopkins University public health summary (2025).

Hantavirus reports in Europe and public health meaning

Separately, global health bodies have noted isolated hantavirus cases in parts of Europe, including recent reports in Spain and France. European hantaviruses (for example, Puumala and Dobrava strains) are rodent-borne and transmitted through contact with infected urine, droppings, or saliva. While most exposures do not cause severe disease, hantaviruses can produce serious respiratory or renal illness in some patients.

Public health prevention centers on rodent control, safe cleanup of contaminated areas, and public awareness. Hantavirus is unrelated to mpox aside from being another infectious threat under surveillance. See the WHO hantavirus fact sheet and CDC hantavirus information for guidance.

Prevention, testing and treatment

Vaccination: The most effective protection for people at higher risk is the two-dose JYNNEOS vaccine series. Public health agencies recommend the vaccine for eligible travelers, some healthcare workers, and others with exposure risks. Clinics and providers are urged to ensure access and completion of the series (see CDC Situation Summary for vaccine guidance).

Testing & treatment: PCR testing of lesion material is standard for mpox diagnosis. Severe cases may be treated with antivirals such as tecovirimat alongside supportive care. Public health advice includes isolation of symptomatic people, careful hygiene, and PPE for caregivers and health workers. For hantavirus, prevention emphasizes rodent control and safe cleanup.

Implications for Huntington Beach, California

Huntington Beach should remain vigilant without panic. The immediate risk to the general public is low, but the city’s reliance on tourism, festivals, and summer gatherings warrants practical preparedness:

• Health and safety for visitors and workers: Review infection-control plans, train staff to recognize symptoms, and promote vaccination among employees at higher risk.
• Vaccination access: Public clinics and some private providers offer JYNNEOS; residents traveling to areas with mpox activity should consider vaccination and complete the two-dose series.
• Protecting vulnerable residents: Parents, caregivers, and long-term care facilities should be alert to symptoms and seek prompt medical advice for suspected exposures.
• Travel and events: Travelers to Europe or areas with Clade I activity should follow guidance, avoid close contact with symptomatic individuals, and consider vaccination.
• Rodent control: Maintain rodent management in parks, beach structures, and storage areas; ensure safe cleanup protocols to reduce hantavirus risk.

Clear public health messaging that emphasizes personal responsibility, vaccination for those at risk, and straightforward prevention steps can help Huntington Beach protect residents and visitors while keeping summer activities open.

Sources and reporting

Primary references and reporting used in this article:

• CDC Situation Summary
• CDC clinical overview (diagnosis, symptoms)
• PMC review of Clade Ib and recent research
• Johns Hopkins University public health summary (2025)
• CDC media release on first U.S. Clade I case (California)
• APIC notice re: CDC advisory
• JAMA retrospective reporting on earlier mpox surveillance
• WHO hantavirus fact sheet
• CDC hantavirus information