Way back in January of 2020, the CDC announced it had found the first case of travel-related COVID in the United States:

The patient from Washington with confirmed 2019-nCoV infection returned to the United States from Wuhan on January 15, 2020. The patient sought care at a medical facility in the state of Washington, where the patient was treated for the illness. Based on the patient’s travel history and symptoms, healthcare professionals suspected this new coronavirus. A clinical specimen was collected and sent to CDC overnight, where laboratory testing yesterday confirmed the diagnosis via CDC’s Real time Reverse Transcription-Polymerase Chain Reaction (rRT-PCR) test.

But a new study looking for evidence of earlier infections suggests there may have been some here as early as mid-December of 2019.

A study published on Tuesday offers new evidence: Based on an analysis of blood tests, scientists identified seven people in five states who may have been infected well before the first confirmed cases in those states. The results suggest that the virus may have been circulating in Illinois, for example, as early as Dec. 24, 2019, although the first case in that state was confirmed a month later.

In the study, published in the journal Clinical Infectious Diseases, Dr. Althoff and her colleagues analyzed blood samples from more than 24,000 people. They found nine people who had donated blood between Jan. 2 and March 18 of last year who appeared to have antibodies to the coronavirus.

Seven of the samples came from blood donated before the date of the first diagnosis in their states — Illinois, Wisconsin, Pennsylvania, Mississippi and Massachusetts.

However, there are some potential problems with this study. First of all, the researchers don’t have travel histories for any of the people involved so it’s hard to know if these seven infections can be traced to travel from Wuhan. Secondly, the initial testing yielded a lot of false positives. The researchers tried to rule these out by testing each sample twice:

The researchers tried to minimize that possibility by using two antibody tests in sequence. The first test flagged 147 samples as possibly having antibodies to the coronavirus; the second slashed that number down to nine.

It seems pretty unlikely that all of those samples were false positives twice in a row but some of them could be. Another possibility is that the positive tests for coronavirus antibodies are reacting to other coronaviruses beside COVID. To rule out this possibility the researchers tested 1,000 blood samples from 2018 and 2019 and got zero positive results. It’s not conclusive but it strongly suggests that the positive results aren’t coming from people who had a common cold.

Finally, this isn’t the first study that has come up with similar findings. Last November a study testing more than 7,000 blood samples taken as early as mid-December 2019 identified 84 cases of people who appeared to have COVID antibodies.

So it appears increasingly likely that some cases of COVID were here in December, well before the first known case was confirmed as arriving in the US on Jan. 15. And that probably means that COVID was spreading more widely than anyone knew in Wuhan in December.

China has claimed the first known person infected with the disease in Wuhan became ill on Dec. 8. However last March the South China Morning Post published an exclusive story claiming government documents suggested the first case went back to mid-November:

According to the government data seen by the Post, a 55 year-old from Hubei province could have been the first person to have contracted Covid-19 on November 17.

From that date onwards, one to five new cases were reported each day. By December 15, the total number of infections stood at 27 – the first double-digit daily rise was reported on December 17 – and by December 20, the total number of confirmed cases had reached 60.

I don’t see that confirmed anywhere and the hunt for patient zero is still officially ongoing, but it’s possible the virus was spreading, both here and there, a month or so earlier than we knew.