Texas issued a statewide flu alert Friday as more confirmed cases of H1N1 virus were reported.
In the alert, the state health department urged all Texans over the age of six months to get a flu vaccine.
At least three people in Harris County have died of the H1N1 virus, officials with the Harris County Institute of Forensic Sciences told reporters. Houston, the fourth largest city of the U.S., is the county seat.
Test results showed the three men died of the H1N1 flu virus, according to the agency's spokeswoman Tricia Bentley. They are the first confirmed H1N1 cases reported in the Houston area.
The death confirmations came after Montgomery County officials confirmed their second case of H1N1 virus Thursday.
Earlier this week, Montgomery County identified the first confirmed case of H1N1 this year. A total of eight patients there were suspected of carrying H1N1 virus. Four of them have already died.
Local media KHOU.COM, quoting unnamed sources, said more than a dozen people have become critically ill from H1N1 in Harris, Montgomery and Jefferson counties.
The website reported Thursday that H1N1 have killed 6 people and left 14 critically ill in the Houston area recently. But the toll could not be verified.
Texas public health officials say every region of the state is seeing intense flu activity this season, which could result, as in past years, in at least several hundred deaths.
In Harris County alone, hospital emergency room visits for flu-like symptoms are at a five-year high.
Official said the virus is the same strain of H1N1 that caused a pandemic in 2009.
Doctors have been seeing hundreds of new flu cases recently in Texas and nationwide.
During the week ending Dec. 7, at least four U.S. states -- Texas, Louisiana, Alabama and Mississippi -- reported high levels of influenza-like illness.
The illnesses started with flu-like symptoms, then progressed to pneumonia and, in some cases, organ failure.