Mpox Clade Ib Strain Spreads Across Several Countries: WHO Issues Update
The WHO reports community transmission of the mpox clade Ib strain in multiple countries, including the United States, Spain, Italy, Portugal, and Malaysia, signaling a renewed global concern.
Introduction
When the global health community started to breathe easier after mpox was declared no longer a public health emergency, a new strain quietly began making its way across continents. The World Health Organisation (WHO) confirmed community transmission of the mpox clade Ib strain in several countries, igniting renewed attention among epidemiologists and public health agencies worldwide.
Background: Understanding Mpox and Its History
Mpox, formerly known as monkeypox, is a zoonotic viral infection caused by the monkeypox virus (MPXV), part of the Orthopoxvirus genus—the same family that includes the smallpox virus. Though smallpox was eradicated in 1980, mpox continues to exist in endemic regions of central and west Africa, especially in the Congo Basin and Nigeria.
The first human mpox case was documented in 1970 in the Democratic Republic of the Congo. Decades later, in 2003, the United States experienced an outbreak linked to imported rodents, marking the virus’s entrance into non-endemic regions. Since then, periodic outbreaks have highlighted the virus’s evolutionary adaptability and its capacity to move beyond its original ecological boundaries.
Following the global mpox outbreak of 2022—driven by clade 2 viruses—WHO declared mpox a Public Health Emergency of International Concern (PHEIC) in August 2024. Although that emergency was lifted in September 2025, the emergence of the clade Ib strain now presents a complex public health question.
New Developments: Clade Ib’s Silent Expansion
In its October 24 update, WHO reported that localized transmission of the mpox clade Ib strain has been detected in the United States, Italy, Spain, Portugal, the Netherlands, and Malaysia. Each of these countries has logged small but concerning numbers of community-acquired cases.
Spain, the Netherlands, and the United States confirmed limited local transmissions without travel links to endemic zones. Italy and Portugal reported three additional infections—again, with no recorded travel history—suggesting community transmission may have begun earlier than detected. Belgium reported a single imported case in a man returning from Malaysia, indicating that transmission chains are now reaching cross-border levels.
WHO experts described the pattern as “widespread yet localized,” cautioning against alarm but emphasizing vigilance.
How Mpox Spreads: Science Behind Transmission
While mpox does not spread easily between people, infection can occur through contact with contaminated materials, body fluids, or lesions. The virus enters through broken skin, respiratory tracts, or mucous membranes. Transmission can also occur via bedding, clothing, or close physical interaction with infected individuals.
Rodents remain a suspected reservoir of the virus, transmitting it to humans through bites or exposure to contaminated excreta. Human-to-human transmission is rare but possible, particularly in domestic or healthcare settings lacking proper infection control.
Symptoms generally begin with fever, headaches, muscle aches, and fatigue, followed by a characteristic rash that evolves through several stages before scabbing and healing. Though most patients recover within weeks, severe illness can develop among immunocompromised individuals or those with underlying conditions.
Expert Insight: Vigilance Without Panic
“Clade Ib does not appear to be more severe at this stage, but geographic spread always demands attention,” said Dr. Mariana López, infectious disease specialist at Spain’s National Centre for Microbiology. “Our goal is containment, not alarm. The data shows mild to moderate clinical presentations in all current cases.”
Public health authorities in the affected nations have increased genomic sequencing and contact tracing efforts. In the United States, the Centers for Disease Control and Prevention (CDC) advised clinicians to remain alert to rashes or febrile illnesses resembling mpox, particularly among individuals with recent international travel.
“It’s a moment to reinforce surveillance infrastructure,” noted Professor David Thorne, an epidemiologist at the University of Oxford. “Viruses like mpox remind us that sustained monitoring and cooperation across borders are key to long-term control.”
Treatment, Prevention, and Public Health Measures
Currently, there is no specific antiviral treatment approved exclusively for mpox. Polymerase Chain Reaction (PCR) testing remains the gold standard for detection. Most cases resolve without medical intervention, though antiviral agents developed for smallpox—such as tecovirimat—are being studied for potential off-label use in mpox management.
The WHO emphasizes community engagement, hygiene, and healthcare training as central to containment. People are advised to avoid direct contact with suspected cases or wildlife sources that may carry the virus. Thorough cleaning of contaminated surfaces and safe handling of linens are also recommended measures.
Vaccines developed for smallpox offer cross-protection against mpox, and some countries have begun limited immunization programs targeting healthcare workers and close contacts of infected individuals.
Global Implications and the Road Ahead
The spread of clade Ib underscores ongoing vulnerabilities in global infectious disease preparedness. As travel resumes and climate-induced ecosystem disruptions bring humans and wildlife into closer contact, new viral spillovers are likely to emerge.
While current cases remain limited, the broader concern lies in undetected community transmission, particularly in regions with limited genomic surveillance capacity. The WHO has urged all countries to share sequencing data and report new cases swiftly, as early detection remains the best defense against a wider outbreak.
“There’s no reason to believe we’re facing another 2022-like scenario,” said Dr. Tedros Adhanom Ghebreyesus, WHO Director-General, during a September briefing. “But complacency would be the wrong lesson. Every outbreak is a test of our global solidarity.”
Conclusion
The reappearance of mpox through its clade Ib variant is a reminder that eradicated threats can reinvent themselves. Though the virus’s spread remains limited for now, its capacity for silent transmission across continents signals a persistent need for international collaboration, scientific vigilance, and community awareness.
The story of mpox continues—no longer a crisis, but a cautionary tale in the delicate balance between nature and human health.
Disclaimer :This article is intended for informational purposes only and should not be used as a substitute for professional medical consultation. For any symptoms resembling mpox, contact a healthcare provider or local health authority.