Per the CBP
You may need a U.S. Department of Agriculture permit and/or a Centers
for Disease Control and Prevention permit to import biological
specimens including bacterial cultures, culture medium, excretions,
fungi, arthropods, mollusks, tissues of livestock, birds, plants,
viruses, or vectors for research, biological or pharmaceutical use.
Permit requirements are located under "Permits" on the USDA Web site
and CDC permit information can be found on the Etiologic Agent Import
Permit Program page.
From the Center for Disease Control Guidance for Importation of Human Remains into the United States for Interment or Subsequent Cremation:
Blood and other body fluids that leak from containers can cause a risk
to human health. CDC has issued guidance for importing human remains
into the United States that are intended for interment (e.g. burial or
placement in a tomb) or subsequent cremation after entry into the
United States. CDC already has regulations that govern importing the
remains of a person who died from a contagious disease that is
This new guidance outlines all of CDC’s requirements about importing
human remains intended for interment or subsequent cremation, no
matter the cause of death. This guidance includes the basic
requirement that all human remains be shipped in a leakproof
Germs that can cause disease could be present in the blood or other
body fluids of a deceased person even if the stated cause of death is
not a contagious disease. Such germs include human immunodeficiency
virus (HIV), hepatitis B virus, hepatitis C virus, and other germs
that can be present in body fluids. This guidance is based on medical
Standard Precautions to prevent exposure to infectious diseases
carried in the blood and other body fluids.
This requirement is intended to protect the public as well as federal,
airline, and airport employees from potential exposure to blood and
other body fluids during transportation, inspection, or storage of
Having said that, the volume of saliva samples you need for a a DNA test is so small I would not worry about it. I would make sure it is in a well sealed container.