A baby from San Luis Potosí in north-central Mexico was likely infected with the 2009 H1N1 influenza virus on 24 February, making this the earliest case of swine flu yet detected.
In an e-mail with ScienceInsider, Celia Alpuche, head of the Instituto de Diagnóstico y Referencia Epidemiologicos (InDRE) in Mexico City, said that her lab had confirmed that the virus had infected a 6-month-old girl who had symptoms of the disease on 24 February, as news outlets had reported . Previously, the earliest case InDRE dated had been to 11 March.
Alpuche said InDRE has confirmed three other cases that had symptoms prior to 11 March: One from Tlaxcala (3 March) and two from Mexico City (8 and 10 March). None of the cases were near Perote, which received a flurry of media attention shortly after the outbreak surfaced because it had what then looked like the earliest cases and the large hog farms in the area.
“We are absolutely done with retesting of all the valid samples we received at InDRE 1 January until now,” Alpuche noted.