In the early days of the pandemic, when much about how SARS-CoV-2 was spread was still very much unknown, consumers were warned to disinfect groceries before putting food onto their shelves or into their refrigerators. But over time, as the respiratory nature of the virus became more fully understood and our focus turned squarely to mask-wearing and social distancing, people eased up on these efforts. Even the World Health Organization and the US Centers for Disease Control reported that the risk of infection from handling packages of food was low. But it may not be as low as we think.

In October, Chinese health authorities discovered live coronavirus on a package of frozen food in Qingdao—the first time active virus was detected on the outside of refrigerated goods. The finding was worrisome, especially when researchers realized the virus on the packaging may be linked to a cluster of new cases in the region. China is one of the only countries to conduct broad inspections of incoming food shipments. Since the inspections started, Chinese authorities have identified the virus on packages of frozen shrimp from Ecuador, squid from Russia, chicken wings from Brazil, and frozen seafood from Norway.

As each new case was discovered, China doubled down on containment efforts, halting some imports, imposing new customs restrictions, and tightening inspections on all food entering the country, where new cases of Covid have been held to under 50 per day for months. Other countries, like New Zealand, have also become newly concerned about the potential risk. In August, after more than one hundred days without any new cases, authorities suspected that a new cluster of infections may have started at a food transport facility with an employee handling frozen foods

A study out of the National University of Singapore confirms contaminated food and food packaging as a potential source of new Covid-19 outbreaks and clusters of infection. The study notes the number of clusters in meat and seafood processing facilities across the world throughout the pandemic, with operations suspending poultry processing plants, tuna canneries, abattoirs, and slaughterhouses around the world. Dale Fisher, one of the authors of the study and the chair of the Global Outbreak Alert and Response Network says it’s possible that contaminated food imports can transfer the virus to workers as well as the environment and frozen food markets may be the first link on a new chain of transmission.

“It’s hitching a ride on the food, infecting the first person that opens the box,” said Fisher in an interview. “It’s not to be confused with supermarket shelves getting infected. It’s really at the marketplace, before there’s been a lot of dilution.”

This finding holds lessons for each of us at every stage of the food supply chain.

At food processing and packaging plants, workers should be given every protection to keep themselves free from infection and to prevent it from spreading to the food—workers should be tested regularly, given financial support if they test positive so they can isolate at home, and have access to masks, glove, sanitizer and disinfectant in the workplace.

Once the food arrives at stores, grocery store workers should be given the same protections to limit the risk of further transmission. And all consumers—whether in countries like the United States where the virus runs rampant, or in places like Taiwan where new infections are near zero—must continue to be vigilant. While many of us continue to close our doors to visitors, we still stock our cupboards with foods from all around the world. Contamination at major food distribution centers raises concerns for all of us around the world. If the virus can be found alive on the outside of frozen food packages, it’s possible that it could be found alive on the inside of those packages as well. It is only prudent then for each of us to approach food handling with caution—wash hands thoroughly after removing food from its package, handle any food carefully before it’s cooked, preferably with gloves, and make sure that all foods are cooked thoroughly, which is certain to inactivate the virus.

This article originally appeared on Forbes.