Oct 14 - US Health Secretary Robert F. Kennedy Jr. has changed how the federal government recognizes deaths from measles in the midst of the worst US outbreak of the highly infectious virus in more than three decades, prompting backlash from disease experts and political opponents. Here is what you need to know about how US measles deaths are currently determined: WHAT HAS CHANGED?

For over a century, US state and local health officials have been required to report cases of death in people with a measles diagnosis to the federal government. These reports are separate from death certificates issued by hospital staff or coroners that can list measles as a cause of death or as a contributing factor.

Disease experts have generally considered the death of any person infected with measles to be related to the virus, which can directly impair organs or exacerbate underlying health problems.

Kennedy has said the US will no longer automatically include state reports to the Centers for Disease Control and Prevention of people who died with measles in the national published tally of measles deaths.

Instead, the CDC's National Center for Health Statistics will first confirm that measles was identified as an underlying cause of death on a person's death certificate — a process that can take weeks, according to health experts. The CDC has also said it was re-evaluating how measles deaths are defined, without explaining the need for such a review. WHY IS KENNEDY'S CHANGE CONTROVERSIAL?

After eradicating measles transmission within the country in 2000, the United States is now battling its biggest resurgence of the virus since 1991, fueled by rising vaccine hesitancy. More than 6,300 infections and at least eight fatalities have been reported by state and local officials since Kennedy, a longtime anti-vaccine activist, took the nation's top health job in early 2025.

Kennedy, who spent years sowing doubt about the measles vaccine — by far the best way to prevent infection and spread of the disease — has cast doubt on whether measles can be fatal and promoted the theory that the virus is less dangerous than the vaccines used against it, contrary to decades of scientific evidence showing the benefits of the shots.

He sparred publicly with Pennsylvania Governor Josh Shapiro, a Democrat, over the state's report of measles-related deaths before changing how such fatalities are counted. The CDC has so far accepted only two out of five measles-related deaths reported by US states so far this year.

Leading medical organizations say Kennedy's comments and policies on immunization have increased Americans' distrust of vaccines, despite decades of evidence showing they are safe and effective at preventing disease. Disease experts say that the health secretary's questioning of measles death reports minimizes the risks of the virus, and that the change in how deaths are counted will delay information that could persuade more families to vaccinate their children. WHY ISN'T IT OBVIOUS WHEN SOMEONE DIED FROM MEASLES?

Many infectious diseases kill indirectly. Measles, for example, can trigger complications such as croup, pneumonia and brain swelling that ultimately prove fatal. In some cases, deadly neurological complications don't appear until years after the infection. The virus can also induce immune system suppression that makes patients vulnerable to fatal secondary bacterial and viral infections.

Death certificates generally record a chain of events. When a patient dies of respiratory failure due to pneumonia that was due to measles, the respiratory failure is the immediate cause of death, and measles is considered an underlying cause because it initiated the sequence of events leading to death.

Local public health officials generally focus on the underlying cause because it reflects the disease responsible for setting the fatal process in motion. WHAT IF THE PERSON HAD OTHER SERIOUS HEALTH PROBLEMS?

When a person with chronic lung disease, cancer, or another condition that makes them especially vulnerable to severe complications dies after a measles infection, the central question is usually whether the death would likely have occurred if the person had not contracted the virus. Investigators must determine whether measles caused the fatal deterioration, merely contributed to it, or was unrelated.

Two experts reviewing the same medical records may sometimes emphasize different aspects of the case. That does not necessarily mean either side is acting improperly. Cause-of-death determinations often involve medical judgment. WHAT IS THE DIFFERENCE BETWEEN A MEASLES DEATH AND A MEASLES-ASSOCIATED DEATH?

The term "measles-associated death" can reflect uncertainty about precisely how much the virus contributed. It allows health officials to acknowledge a connection when multiple factors were involved. ARE MEASLES DEATHS BEING OVERCOUNTED?

There is no evidence that measles mortality is systematically overcounted. Historically, public health surveillance has focused on whether a disease caused or substantially contributed to death, rather than whether it was the sole factor involved.

During the height of the COVID-19 pandemic, a similar debate took place over whether patients with preexisting chronic diseases were dying from COVID — that is, the SARS-CoV-2 virus caused the death — or with COVID, meaning they happened to have COVID but their cancer or other health condition is what killed them.

Public health experts argue that excluding deaths simply because a patient had other medical problems would underestimate the disease's impact.