Pandemic & Infectious Disease — 2026-04-04

Active Outbreak Tracker

Mpox (Clade I) — Democratic Republic of Congo

• Status: Outbreak declared over; more than 2,200 suspected deaths over two years
• Key Development: Congo officially announced the end of a two-year mpox outbreak this week. The outbreak, driven by clade I mpox, is believed to have caused over 2,200 deaths — making it one of the deadliest mpox outbreaks on record. The declaration marks a significant public health milestone, though health authorities caution that vigilance must be maintained.
• Response: National and international health authorities have been engaged in containment and vaccination efforts throughout the outbreak. A Phase II clinical trial of the mpox treatment NV-387 (by NanoViricides) is expected to commence soon in the DRC, continuing post-outbreak research efforts.

Measles — Global

• Status: Active and accelerating; at least 46 children dead in 2026, cases surging globally
• Key Development: A new analysis published this week highlights why measles is resurging in 2026, pointing to dangerous immunity gaps as the primary driver. The outbreak is being tracked across multiple continents, with vaccination coverage having dropped in the wake of COVID-19 disruptions and ongoing humanitarian crises. Experts warn that immunity gaps accumulated over several years are now producing larger and more deadly outbreaks.
• Response: WHO and CDC continue to monitor global measles trends. The CDC's global measles vaccination data channel is tracking the top 10 countries with active measles outbreaks worldwide.

1 sources

earthtimes.org

earthtimes.org

Respiratory Viruses (COVID-19, Flu, RSV) — United States

• Status: Low activity nationally; 2025–2026 respiratory season winding down
• Key Development: The CDC updated its respiratory virus activity data as of today, with current surveillance showing low spread of COVID-19, influenza, and RSV across the United States. The agency has indicated it does not anticipate producing additional seasonal outlook updates for the remainder of the 2025–2026 respiratory season, suggesting the threat window is closing.
• Response: California continues RSV immunization with monoclonal antibodies (nirsevimab and clesrovimab) for eligible infants and children through April 30, 2026. CDC's national tracking infrastructure remains active.

Vaccine & Treatment Pipeline

• WHO Immunization & Vaccines Director's Message — March 2026 (WHO): In a message published April 2, 2026, WHO's Department of Immunization, Vaccines and Biologicals director warned of "sudden reductions and changes in financial resources, rapidly escalating conflicts, increasing numbers of humanitarian and fragile settings, evolving disease threats, and increasing programmatic complexity." The WHO's Strategic Advisory Group of Experts (SAGE) stressed the critical importance of strong vaccination programs in this environment.

• Next-Generation COVID-19 mRNA Vaccines (Multiple developers): A tracker published April 2, 2026 by PLOS Absolutely Maybe reports that several next-generation COVID-19 vaccines — including self-amplifying mRNA and mucosal immunity approaches — are now advancing into mid- or late-stage trials. A Phase 3 trial published in npj Vaccines found that self-amplifying COVID-19 mRNA vaccination induces longitudinally enhanced antibody function.

• NV-387 Mpox Treatment (NanoViricides): On April 1, 2026, NanoViricides announced that a Phase II clinical trial of NV-387 for mpox treatment is expected to begin soon in the DRC. Clinical trial site preparations are underway. The trial moves forward even as Congo has declared its clade I outbreak over, underscoring the need for approved antivirals for future outbreaks.

• Q2 2026 FDA Decisions (Multiple): A roundup published today by HCPLive identifies six FDA decisions to watch in Q2 2026, listed chronologically by expected decision date, spanning infectious disease and other therapeutic areas.

2 sources

who.int

who.int

who.int

who.int

Expert Analysis

The 2026 measles resurgence has become a defining story in global infectious disease, and it is not happening in a vacuum. According to reporting published within the past 24 hours by Earth Times, at least 46 children have already died in the current outbreak wave, which experts attribute to immunity gaps that widened during the COVID-19 pandemic and have never been fully closed. Mass vaccination campaigns were disrupted from 2020 through 2022, creating cohorts of unvaccinated or under-vaccinated children now reaching the age of highest measles vulnerability.

The broader systemic threat to immunization programs was placed in sharp relief this week by WHO's Department of Immunization, Vaccines and Biologicals. In an April 2 message, the department's director described a "global context marked by sudden reductions and changes in financial resources, rapidly escalating conflicts, increasing numbers of humanitarian and fragile settings, evolving disease threats, and increasing programmatic complexity." The director warned that SAGE has "stressed the critical importance of strong" vaccination systems in precisely these conditions — a message with urgent implications for measles and beyond.

Meanwhile, pandemic preparedness experts are sounding the alarm ahead of the 2026 UN High-Level Meeting on pandemic prevention, preparedness, and response (PPPR). A recent Lancet commentary argues that spillover prevention — stopping pathogens from jumping from animals to humans in the first place — must be elevated in the global political agenda. The authors note that "global attention has waned amid inflation, war, and challenges" since the COVID-19 pandemic, and warn that the world risks repeating the same unpreparedness cycle without structural reform.

Global Health Security

Europe's infection prevention landscape is the subject of a forward-looking analysis published by Medscape (April 3, 2026), which models six possible futures for the continent through 2040. The analysis finds that whether Europe succeeds or fails at infectious disease control will hinge on "closer cooperation, trusted data sharing, and community-centered prevention" — and that fragmentation and underfunding of public health infrastructure represent the primary risks. The piece comes as European health agencies continue to grapple with post-pandemic restructuring.

The 2026 UN High-Level Meeting on Pandemic Prevention, Preparedness, and Response (PPPR) is emerging as a critical policy moment. The Lancet's recent commentary calls on member states to formally integrate zoonotic spillover prevention — the upstream blocking of animal-to-human pathogen transmission — into any agreed PPPR framework. Authors argue that without this, response-only investments will remain reactive and insufficient.

WHO's SAGE continues its work ahead of the May 2026 deliberations on COVID-19 vaccine antigen composition, having recently posted formal data requests. TAG-CO-VAC is closely monitoring SARS-CoV-2 variant evolution and vaccine performance against circulating strains to inform updated recommendations — a process that will shape booster formulations globally for the coming year.

What to Watch Next

• May 2026 COVID-19 vaccine antigen composition decision: WHO's TAG-CO-VAC is currently soliciting data on SARS-CoV-2 variant evolution and vaccine performance ahead of May deliberations. The outcome will determine which strains are targeted in the next round of updated COVID-19 boosters — a decision that affects hundreds of millions of people globally.

• Measles outbreak trajectory: With 46 children already dead and immunity gaps still widening in fragile and conflict-affected settings, global measles case counts will be closely watched in the coming weeks. Any expansion into new geographic areas or age groups would signal a worsening crisis requiring emergency vaccination response.

• NV-387 Phase II mpox trial launch in DRC: NanoViricides has announced imminent trial initiation for its mpox antiviral NV-387 in the DRC. The launch timing — just as Congo declared its clade I outbreak over — raises questions about enrollment and will test whether post-outbreak research momentum can be maintained. Results could yield the first approved mpox-specific antiviral treatment.