Early US Flu Wave Hits West Coast as Holiday Travel to Mexico Peaks

An unusually early flu season is spreading along the US Pacific coast, driven by a mutated influenza A strain, just as travel from the United States to Mexico picks up for Día de Muertos, the holidays and the winter snowbird season. As of early October, Mexico’s Health Ministry had not detected the new mutation in the country, according to Mexico News Daily.

The US accounts for 67.1% of international travel into Mexico, with 19 million visitors expected this year, the outlet reported. Those trips peak from late October through January, the same months when flu levels run highest.

What is different about this flu season

US flu seasons usually begin in the South, in states such as Florida, and then spread through fall and winter. This year, states along the Pacific, including Hawaii, are already seeing flu levels normally reached in December or January.

Hawaii’s latest positive flu test rate is 27.1%, compared with 5.6% at the same point last year. California and Washington both have positivity rates above 11%.

The strain appears to have come from Asia. It is a mutated version of H1N1, a subtype of influenza A, carrying a change called G155E that can slip past immunity people already have. Japan first detected the mutation in May and is now seeing fast-spreading outbreaks among children that have closed schools. H1N1 itself first emerged in 2009 in La Gloria, Mexico, and caused a pandemic that mostly hit children.

Mexico had a wave of off-season flu over the summer, but it was mostly influenza B. No G155E cases have been identified in Mexico so far.

Who is most at risk

Teenagers and young adults appear to produce a weaker antibody response to the mutated strain, so it may spread more easily among them. There is no evidence so far that it causes more severe illness.

The groups at highest risk of severe flu are the same as in earlier seasons, and they get priority for free flu shots in Mexico:

• Children 6 to 59 months old
• Adults 60 and older
• Pregnant people
• People ages 5 to 59 with chronic conditions such as diabetes, high blood pressure, heart, lung or kidney disease, cancer or HIV
• Healthcare workers

People with disabilities, residents of long-term care facilities and people with weakened immune systems are also considered at higher risk, but they are not in the priority group for free shots.

What it means for residents and visitors in Mexico

Health officials in both countries are urging people to get vaccinated early, because the body needs about two weeks after a shot to build immunity. Getting the shot now would put that protection in place before holiday travel and gatherings.

The Health Ministry (Secretaría de Salud) opened its National Vaccination Campaign for the 2026-2027 fall and winter season on Oct. 12. It runs until March 31, 2027, and aims to give more than 50 million doses of vaccines against COVID-19, influenza and pneumonia. Mexico gives out 30 million flu vaccines in a typical year.

For the first time, the campaign also offers the respiratory syncytial virus (RSV) vaccine to pregnant women between 32 and 36 weeks of pregnancy, to protect babies in their first months. RSV usually causes mild cold symptoms but can put infants and some older adults in the hospital.

Where to get a shot

Free shots are given at local health clinics and public gathering places across Mexico. The Health Ministry’s interactive map at dondemevacuno.salud.gob.mx lists nearby sites, and the toll-free number 079 gives information on where vaccines are available. People outside the priority groups can buy flu shots at private pharmacies and hospitals.

Source: Mexico News Daily