A woman in Pennsylvania has become the sixth American to die after contracting measles this year, as the death toll linked to the virus hits its highest level since 1991.

In a statement posted to Facebook, Franklin County Coroner's Office in Pennsylvania said that the 39-year-old had a measles infection and several underlying health conditions.

The office said: 'This is the first death in Franklin County in many years with a recent history of measles diagnosis and meets the definition set forth by the Pennsylvania Department of Health for a measles-associated death.'

No further details were revealed, which the office said was to protect the patient's privacy. It was not clear whether she had been vaccinated.

The fatality takes the US toll of deaths linked to measles to its highest level in 35 years, after an outbreak in 1991 killed at least 13 people. 

Measles cases are also at a 35-year high. Data from the Centers for Disease Control and Prevention (CDC) show 4,080 measles infections have been recorded in the US so far this year, the most since 1991 when 9,643 infections were recorded.

Pennsylvania is the hardest-hit state, recording more than a quarter of all infections nationwide. To date, it has registered 1,136 measles cases and 219 hospitalizations. A third of the state's cases are in children under 18 years old and fewer than one percent of patients were vaccinated. 

Measles cases have been recorded in 45 states nationwide, with only Arkansas, Hawaii, Mississippi, New Hampshire and Nevada yet to record an infection. 

The announcement of the newest measles-linked death comes amid tension between state and federal health authorities over the 2026 measles death toll. 

While this is the sixth measles-linked death recorded in Pennsylvania, the CDC has only recognized two deaths attributed to the disease so far this year. 

It is yet to include the other four deaths that had previously been reported by health officials in Pennsylvania. 

No further details were given by the CDC on the measles-linked fatalities. 

According to state health officials, the five fatalities previously recorded were all in Pennsylvania.

State health authorities said that those who died after contracting measles were two infants and a resident in Lancaster County, an 18-year-old in Mifflin County and a 40-year-old in Jefferson County.

Measles is one of the most infectious diseases known to man – for unvaccinated people, nine in 10 of those exposed to the virus will get infected.

In many cases it causes a cough, fever and a distinctive angry red rash that starts on the face before spreading across the whole body.

Children under five years old and people who have weakened immune systems are particularly at risk from the disease.

About one in five unvaccinated people who contract measles are hospitalized, while one in 20 children who catch the disease develop pneumonia, a potentially fatal infection in the lungs, the CDC says.

About one out of every 1,000 children who catch measles also develop encephalitis, or swelling of the brain, which can cause convulsions and leave children deaf or with an intellectual disability. 

Nearly one to three out of every 1,000 children who are infected with measles die from respiratory or neurological complications. 

Doctors say the best way to prevent a measles infection is to get vaccinated.  

The measles, mumps, and rubella vaccine (MMR) vaccine, which is administered once between ages 12 and 15 months and again between ages four and six, is thought to be 97 percent effective in preventing measles, according to the CDC.

Before MMR vaccines became available in the 1960s, measles caused epidemics with up to 2.6 million global deaths every year. By 2023, that number had fallen to roughly 107,000 deaths. 

Nationwide, 92.4 percent of kindergarteners are fully vaccinated against measles, below the CDC's 95 percent threshold for herd immunity. In Pennsylvania, the MMR vaccination rate is 94.6, while rates in Maryland and Iowa are 96 and 90 percent, respectively. 

Exemptions are also on the rise at 4.2 percent, up 17 percent from 1.6 percent just over a decade ago.