Dhillon is an instructor in the Division of Global Health Equity at Brigham and Women’s Hospital and Harvard Medical School. Karan is an infectious disease physician and epidemiologist at Stanford University. Srikrishna is founder of Patient Knowhow.

Germany reported an outbreak of highly pathogenic H5N1 bird flu on a farm in the eastern region of Saxony near the border with the Czech Republic, the World Organisation for Animal Health (WOAH) said on Monday.

In what could be the first cases of bird flu spreading between humans in the United States, a group of potential H5N1 infections in Missouri has now grown to eight.

"Even sporadic cases of human-to-human transmission indicate a big change in the virus and suggest it is exploring new directions in virus evolution that bring it closer to a pandemic virus," James Lawler, MD, MPH, of the University of Nebraska Medical Center's Global Center for Health Security, previously told MedPage Today.

Seven people in contact with a patient hospitalized with bird flu also developed symptoms, the C.D.C. reported. Some are undergoing further tests.

At least one household member and six healthcare workers who encountered the index case-patient are being investigated after showing symptoms of viral infection.

At least eight people may be infected with H5N1 bird flu in Missouri, marking the first cluster of the disease spreading between humans in the United States. The first case of a human contracting bird flu with no known animal contact happened in Missouri in August,