Virus World

Testing conducted by the FDA on pasteurized commercially purchased milk has found genetic evidence of the H5N1 bird flu virus, the agency confirmed Tuesday. But the testing, done by polymerase chain reaction, or PCR, cannot distinguish between live virus or fragments of viruses that could have been killed by the pasteurization process. The agency said it has been trying to see if it could grow virus from milk found to contain evidence of H5N1, which is the gold standard test to see if there is viable virus in a product. The lengthy statement the agency released does not explicitly say FDA laboratories were unable to find live virus in the milk samples, but it does state that its belief that commercial, pasteurized milk is safe to consume has not been altered by these findings. “To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the statement said.

The document was long on assurances but short on details of what has been undertaken or found. It does not specify how many commercial samples were taken or in how many markets, nor does it indicate what percentage of the samples were PCR-positive for H5N1. The statement did not indicate if the testing suggested the amounts of viral genetic material in the milk were low or high. Furthermore, the statement did not reveal if the milk products were purchased in parts of the country where outbreaks have occurred, or in areas where cows haven’t been seen to have been infected. The FDA did say it is testing milk from infected animals, in the processing system, and from store shelves with the goal of producing a “large representative national sample” of the milk supply. Beyond assessing the safety of the supply, such a sample could enable the agency to construct a more robust picture of H5N1’s spread among dairy cows nationally. The agency emphasized that testing of commercially available milk is ongoing, and this includes efforts to discern any potential differences between different dairy products, such as cream and whole milk....

It remains unclear whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be shed into breastmilk and transmitted to a child through breastfeeding. Recent investigations have found no evidence of SARS-CoV-2 in human breastmilk, but sample sizes were small.

We examined milk from two nursing mothers infected with SARS-CoV-2. Both mothers were informed about the study and gave informed consent. Ethical approval for this case study was waived by the Ethics Committee of Ulm University and all samples were anonymised. Clinical data and the timecourse of infection in the two mothers is shown in figure 1. After feeding and nipple disinfection, milk was collected with pumps and stored in sterile containers at 4°C or −20°C until further analysis. We determined viral loads using RT-qPCR for SARS-CoV-2 N and ORF1b-nsp14 genes, in both whole and skimmed milk (obtained after removal of the lipid fraction). 

We detected SARS-CoV-2 RNA in milk samples from Mother 2 for 4 consecutive days. Detection of viral RNA in milk from Mother 2 coincided with mild COVID-19 symptoms and a SARS-CoV-2 positive diagnostic test of the newborn (Newborn 2). Mother 2 had been wearing a surgical mask since the onset of symptoms and followed safety precautions when handling or feeding the neonate (including proper hand and breast disinfection, strict washing, and sterilisation of milk pumps and tubes). However, whether Newborn 2 was infected by breastfeeding or other modes of transmission remains unclear. Further studies of milk samples from lactating women and possible virus transmission via breastfeeding are needed to develop recommendations on whether mothers with COVID-19 should breastfeed.

Published in The Lancet (May 21, 2020):

https://doi.org/10.1016/S0140-6736(20)31181-8

U.S. regulators confirmed that sick cattle in Texas, Kansas and possibly in New Mexico contracted avian influenza. They stressed that the nation’s milk supply is safe. A highly fatal form of avian influenza, or bird flu, has been confirmed in U.S. cattle in Texas and Kansas, the Department of Agriculture announced on Monday. It is the first time that cows infected with the virus have been identified. The cows appear to have been infected by wild birds, and dead birds were reported on some farms, the agency said. The results were announced after multiple federal and state agencies began investigating reports of sick cows in Texas, Kansas and New Mexico. In several cases, the virus was detected in unpasteurized samples of milk collected from sick cows. Pasteurization should inactivate the flu virus, experts said, and officials stressed that the milk supply was safe.

“At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health,” the agency said in a statement. Outside experts agreed. “It has only been found in milk that is grossly abnormal,” said Dr. Jim Lowe, a veterinarian and influenza researcher at the College of Veterinary Medicine at the University of Illinois at Urbana-Champaign. In those cases, the milk was described as thick and syrupy, he said, and was discarded. The agency said that dairies are required to divert or destroy milk from sick animals....

USDA report (March 25, 2024):

https://www.aphis.usda.gov/aphis/newsroom/news/sa_by_date/sa-2024/hpai-cattle