There are three cases of person-to-person transmission of SARS-CoV-2, the coronavirus that causes COVID-19, in the United States, according to the Centers for Disease Control and Prevention (CDC). This includes a patient in intensive care in Sacramento County in California, but it does not include 44 people from the Diamond Princess cruise ship that have tested positive. A British man who was also quarantined on the ship recently died, bringing the ship's death toll to six.

The CDC announced the California case late Wednesday. How this patient came in contact with the virus is unknown, as they had not traveled anywhere the virus is in outbreak and had not knowingly come into contact with anyone who had traveled. Nancy Messonnier, Director of the Center for the National Center for Immunization and Respiratory Diseases (NCIRD), a department within the CDC, said that they are expecting to monitor family members of the patient and health care workers who came in contact with the patient for spread of the virus.

California governor Gavin Newsom said that they are monitoring 8,400 people for presence of the virus and have only 200 kits available to make confirmatory diagnoses.

Yesterday, Representative Ami Bera (D, CA-7), who represents parts of Sacramento County near to where the patient is, said that there was a four day gap in the federal government's response to a request from local medical officials for COVID-19 testing for the patient. The CDC reiterated their claim that they were first contacted on the 23rd, as opposed to Rep. Bera's claim that Sacramento County officials contacted them on the 19th. The CDC stated that they received samples from the patient on the 25th and confirmed the presence of the virus on the 26th. No explanation for the discrepancy was offered by the CDC.

The CDC expressed confidence that aggressive border control played a part in keeping US cases low. California governor Gavin Newsom said that they are monitoring 8,400 people for presence of the virus and have only 200 kits available to make confirmatory diagnoses.

Kits made available by the federal government to diagnose COVID-19 use the polymerase chain reaction (PCR), a method for detecting the presence of specific sequences of DNA or RNA. The kit contains three different "primer" sets (small pieces of DNA that stick to specific regions of the virus' genome), all three of which need to return positive results to confirm presence of coronavirus. One primer set has already been found to not work in testing. The CDC then announced that two positive results are enough, though some labs stated that a second primer set is also unreliable, and are now making their own kits instead.