Laboratory-confirmed and probable cholera cases along the Iran-Iraq returnee corridor passed 6,000 on Wednesday with at least 71 deaths recorded, the World Health Organization said, as a cross-border oral vaccination campaign reached the halfway mark of its 1.6 million-dose target and the first measurable slowing of new admissions began to show up in the largest reception camps.

In a midmorning briefing from Cairo, the WHO’s Eastern Mediterranean regional office said 6,184 cases had been logged across Iran’s Ilam and Kermanshah provinces and Iraq’s Diyala and Maysan governorates as of Tuesday evening, more than four times the toll reported in the same agency’s first formal alert on April 26. Deaths were running at roughly 1.1 percent of confirmed cases, lower than the early days of the outbreak but still above the regional baseline of recent years.

“We are seeing the first signs that the curve is bending in three of the eight priority districts, and those are the districts where we got water in early and vaccines in by Friday,” said Dr. Hanan Balkhy, the WHO’s Eastern Mediterranean regional director, who returned to Geneva from a five-day field mission late Monday. “Where the chlorination came in late, or where the population is still on tankered water, we are not bending anything yet.”

UNICEF said the vaccination campaign, drawing from the global oral cholera vaccine stockpile released by the International Coordinating Group on Vaccine Provision in Geneva, had administered approximately 802,000 doses across 38 fixed and 22 mobile sites since the first vials moved through Baghdad and Kermanshah airports a week ago Monday. Roughly 60 percent of recipients had been children under fifteen or adults over sixty, the agency said, in line with the prioritization protocol agreed with Iranian and Iraqi health authorities.

The most encouraging trend, officials said, was at the Karim Khan reception camp outside Khanaqin, which served as the outbreak’s earliest large cluster. New admissions to the camp’s cholera treatment center peaked at 184 patients on April 30 and had fallen to 71 on Tuesday, according to figures shared by the Iraqi health ministry’s outbreak response unit in Baquba. A second large cluster near Badra, on the Mehran corridor, was tracking about four days behind that curve and was expected to peak this week.

On the Iranian side, the provincial health directorate in Ilam said it had confirmed 2,140 cases across seven transit and reception points, with the heaviest concentration still around the badly damaged outskirts of Mehran town. State media in Tehran reported that the country’s national pharmaceutical company had delivered more than 4.2 million sachets of oral rehydration salts to provincial warehouses since April 27 and that intravenous fluid production lines had been running on three shifts.

“What we are doing now is a race between the vaccine, the chlorination teams and the start of the hot season,” said Dr. Karim Soltani, an epidemiologist with the WHO’s Tehran country office, in a telephone interview from Ilam. “If we keep ahead of those three lines for the next two weeks, we contain this to a bad outbreak. If any one of them slips, it becomes a regional public-health emergency.”

Officials cautioned that the case totals likely undercounted true transmission by a meaningful margin. Surveillance remained patchy in smaller informal settlements outside the formal camp system, and several Iraqi border communities had not yet been integrated into the WHO’s daily reporting feed. A senior Iraqi health official, speaking on condition of anonymity because the figures were not yet public, said internal modeling at the ministry was assuming roughly 1.8 cases in the field for every laboratory-confirmed case in the system.

Water and sanitation gaps remain the central concern. The two main water-treatment plants damaged during the war’s middle weeks — one in the Mehran corridor and one outside Khanaqin — are not expected to return to even partial service before late May, according to engineers contracted by the United Nations Development Programme. In the meantime, UNICEF said it had now positioned eleven mobile water-treatment units across the affected districts, producing a combined 920,000 liters of safe drinking water per day, and had distributed roughly 380,000 household water-treatment kits.

International funding for the response has begun to firm up, though officials said it remained well short of the agencies’ combined appeal. The European Union on Tuesday announced an additional 48 million euros for the WHO and UNICEF cholera operation, on top of the 30 million euros pledged at last week’s Brussels donor call. Canada, Norway, Japan and South Korea each added smaller commitments, bringing the total of fresh post-April pledges to roughly 240 million dollars. The United States has earmarked a portion of the pending Iran war supplemental for humanitarian response in the corridor, though the bill remains tied up in House negotiations.

“This is not the moment to declare victory because one camp’s curve is bending,” said Layla Hassan, a Beirut-based regional analyst at the Carnegie Middle East Center, in a phone interview. “Cholera outbreaks at this scale tend to oscillate. You bend the curve in week three, you think you have it, and then a heatwave or a sandstorm or a power cut at a chlorination plant reseeds the whole system. The fundamentals here are still fragile.”

Public-health authorities in both countries said they were preparing for a second wave of transmission risk tied to the expected onset of summer heat across the corridor by late May, when temperatures in Diyala routinely top 40 degrees Celsius and water demand spikes. The WHO said it would begin scenario planning with Iranian, Iraqi and Gulf donors next week for a possible second tranche of vaccine deployment focused on districts not covered in the current round.

For families in the camps, the daily reality has been a slow shuffle of queues — for rehydration salts, for vaccination cards, for the chlorinated water trucks that arrive at varying hours. At a tent clinic outside Mehran on Tuesday, Fatima Karimi, a 34-year-old returnee from western Tehran province whose youngest daughter had been treated for moderate dehydration the day before, said the family had been told to remain in the camp another ten days before attempting to return home. “She drank from a tank we trusted,” Karimi said. “We will not do that again.”

UNICEF and the WHO said the next milestone for the campaign would be hitting one million doses administered by Sunday and a fuller assessment of district-level transmission by midweek. Officials said additional vaccine releases from the Geneva stockpile and further mobile water-treatment deployments would be announced as new field data came in.