Flu virus can be transmitted from an infected mother to offspring through breast milk and infected offspring can transmit the flu virus to the mother through the breast cells the infants come in contact with while nursing. Alyson Kelvin, from the University Health Network, Toronto, Canada, and colleagues the first to prove that flu virus can be transmitted through breast cells.
The study was conducted with ferrets. Ferrets have been shown to be as susceptible to flu virus as humans. The pathways of flu transmission are known to be similar in humans and ferrets. The researchers selectively introduced the 2009 H1N1 strain of influenza virus to some ferret mothers and to some ferret infants that were four weeks of age. Flu was transmitted to the infants from infected mother and flu was transmitted to the uninfected mothers from infected infants. The most likely point of contact and flu transmission was the nipple.
The researchers found that mothers that had only one breast infected with flu transmitted flu to their offspring through that breast only. Laboratory studies of a similar pathway of transmission of the flu virus in cultured human breast tissue were inconclusive. Human breast tissue in a cultured environment normally shut down milk production before the potential to transmit the flu virus was possible.
The researchers show that the potential for transmitting the flu virus through breast tissue or breast milk in humans is possible. The upcoming flu season is an urgent time for women that are breast feeding to have a flu inoculation as well as their children. The discovery poses a significant problem for third world countries where flu vaccines are not always plentiful and where substitutes for breast milk are not available.