A health worker contracted Covid-19 and then infected his family who are based in Leone who attended several gatherings over the weekend including church.
American Samoa is in Code Red - meaning people must stay home, be vaccinated, wear masks and only essential services are open.
RNZ Pacific Correspondent in Monica Miller said there was a lot of panic buying when people found out Monday night.
"All this time American Samoa has managed to ward of any community spread. It is a feeling of disbelief. How did we get to this when everything was followed. They were very strict. The fact that it turns out not to be a traveller but an employee of the department of health."
She said 80-percent of America Samoa is fully vaccinated.