The outbreak of the world’s most infectious disease that began in West Texas has officially spread to a major city.

Health officials reported yesterday that two measles cases detected in the Dallas-Forth Worth area, home to nearly 8million people, had been linked to the outbreak that has infected hundreds and killed two children.

One case was in Collin County, which includes the suburbs of Plano and Frisco, while the other was in Rockwall County, on the edge of the metropolis.

No further details were released on the patients, including their ages, vaccination status, how they were infected, or whether they passed the disease to others. 

But the infections have triggered alarm, especially given that the city has daily flights to other major cities including Los Angeles, New York, Houston and Chicago.

The report comes barely a week after the US officially reported 1,000 measles cases this year — marking only the second time case counts have crossed this threshold since the disease was declared eradicated in 2000.

Officials are warning if the disease continues to spread unabated, the US could lose its measles elimination status.

Pictured above is the skyline in Dallas, Texas, which forms part of the Dallas-Fort Worth area (stock)

The Texas Department of Health revealed the two new cases in an update released on its dashboard Tuesday.

Seven measles cases have been reported in the Dallas-Forth Worth area – Dallas is the ninth largest city in the US – since the outbreak began in January.

The five others have not been linked to the major outbreak, and are said to be due to people catching the virus from other sources.

Collin County officials warned residents of a potential measles exposure on April 10 and 11, saying a patient visited several locations in Plano while infectious. 

These included a Walmart, Ross Dress for Less and a Dollar Tree.

And in a warning on April 16, Rockwall County officials reported an individual who had tested positive for measles after recently traveling to West Texas. 

They said the patient was at home for most of their infectious period, and is now no longer infectious and has since recovered.

Vaccination rates in the affected counties are as low as 92 percent, below the 95 percent experts say is needed to establish herd immunity.

In Collin county, data shows 93.3 percent of kindergarteners were vaccinated against measles in 2023 and 2024, the latest data available.

While in Rockwall county, fewer than 92 percent of kindergarteners were inoculated against the disease.

A total of 717 measles cases have been reported in the Texas outbreak since January, making it the largest to rock the US since the disease was declared eliminated.

There were more measles cases — 1,061 infections — recorded in a cluster in New York in 2019, but officials say this was due to people returning from abroad infected with measles and then passing on the disease. 

A total of 93 patients in the Texas outbreak have been hospitalized with the disease since the spread began, while nearly all the cases have been among people under 18 who were unvaccinated.

The outbreak has already spread to at least nine other states, including neighboring New Mexico — reporting 71 cases — and Oklahoma — reporting 16 cases.