A fast-moving influenza outbreak, vaccine shortages and polluted air are colliding to challenge the country’s health system.

This autumn, influenza arrived earlier than many doctors expected. By mid-November, hospitals across Iran were already seeing a steady rise in patients with fever and respiratory symptoms. Laboratory testing soon confirmed what physicians suspected: the H3N2 strain of seasonal influenza had begun spreading rapidly.

According to official figures from Iran’s Ministry of Health, the outbreak has already been linked to more than one hundred deaths. Hospitals in several provinces report increasing pressure on emergency wards and respiratory units.

The timing has made the situation more complicated. The influenza wave has coincided with repeated episodes of severe air pollution in many of Iran’s largest cities—conditions that can aggravate respiratory disease and make infections harder to recover from.

An early start to the season

In a typical year, influenza activity in Iran begins to climb gradually during the colder months. This year, the increase came sooner and more sharply.

Health officials say the H3N2 strain appears to be circulating widely across multiple regions of the country. While influenza often affects elderly patients and people with chronic illnesses most severely, doctors report that a noticeable number of younger adults have also required medical care.

Authorities have said that many of the people who died had not been vaccinated against influenza, although detailed national data on vaccination coverage remains limited.

When polluted air meets respiratory illness

At the same time that influenza cases were rising, air quality in cities such as Tehran, Isfahan and Mashhad repeatedly reached unhealthy levels.

International studies have shown that exposure to fine particulate pollution—especially particles smaller than 2.5 micrometres, known as PM2.5—can increase the risk of complications from respiratory infections. Irritated lung tissue becomes more vulnerable to viral damage, and hospital admissions for respiratory illness often rise during periods of heavy pollution.

The coincidence of these two factors—polluted air and a fast-moving influenza strain—has created difficult conditions for public health authorities.

Reports from several provinces

Health authorities across the country describe similar patterns.

In Yazd province, local officials say more than 1,000 confirmed influenza infections have been recorded since the start of the season. In the southern province of Hormozgan, several deaths have been reported, including that of a young adult whose condition deteriorated rapidly despite having no known underlying illness.

Hospitals in other regions have also reported an increase in admissions linked to influenza and related respiratory complications.

A global surveillance network behind the scenes

Seasonal influenza outbreaks may appear local, but they are monitored through an international scientific system.

Iran’s National Influenza Center participates in the World Health Organization’s Global Influenza Surveillance and Response System (GISRS). Laboratories around the world contribute viral samples and genetic data to the network, allowing scientists to track how influenza viruses evolve and spread.

Those data are also used to determine the composition of seasonal influenza vaccines each year.

In late November, a World Health Organization emergency health team visited Iran’s influenza laboratory to review monitoring procedures and diagnostic capacity—part of routine global cooperation aimed at detecting new strains quickly.

Vaccination and access

Influenza vaccination has become a renewed topic of debate during the current outbreak.

Public health officials say vaccination rates among high-risk groups remain uneven. Estimates suggest that roughly a third of older adults received influenza vaccines this season, while coverage among pregnant women is considerably lower.

Availability is one reason. Pharmacies in several cities report that vaccine supplies were quickly depleted. Cost is another factor: influenza vaccines are not universally covered by insurance, and prices can be high relative to household income.

For some people, obtaining a vaccination has therefore been difficult, even when they intended to receive it.

The scientific difficulty of H3N2

Influenza vaccines are reformulated each year to match circulating strains. For the 2025–2026 influenza season, the World Health Organization recommended a vaccine targeting H1N1, H3N2 and B/Victoria lineages.

H3N2 has long been one of the more challenging influenza viruses to control. It undergoes frequent genetic changes—known as antigenic drift—that can allow the virus to partially evade immunity generated by previous infections or vaccination.

Because of this, vaccine effectiveness against H3N2 often varies from season to season. Even when protection is incomplete, however, vaccination significantly reduces the risk of severe illness and hospitalization.

A winter still ahead

Health officials expect influenza activity to continue through the colder months. If cold weather coincides with continued air pollution, respiratory illnesses could remain a serious burden for hospitals.

Public-health advice remains familiar: vaccination for high-risk groups, avoiding crowded indoor spaces when ill, wearing masks in poorly ventilated environments, and seeking medical care if severe symptoms appear.

These measures may sound routine. In a heavy influenza season, they can make a real difference.