Infection cases are among the most, if not the most, difficult type of medical malpractice cases. This is because in order to prove negligence, the plaintiff must usually prove how they became infected. Proving the origin of an infection is very difficult.

For example, epidemiological research in the past concluded that pertussis, or whooping cough, was primarily transmitted between mother and baby. While pertussis is usually only a nuisance to children and adults, it can be fatal for babies. Since newborn babies are particularly susceptible to pertussis, because they cannot receive the DTaP vaccine (diphtheria-tetanus-acellular pertussis) for the disease until they are two months old, knowing the primary form of transmission is important to prevention.

The two months between birth and when a baby can receive the DTaP vaccine is also the time when a baby is most likely to die from a pertussis infection. Currently, the best protection, really the only protection, during a baby’s first two months is the limited transfer of antibodies from mothers who get the Tdap, vaccine booster, toward the end of their pregnancy, and keeping the baby away from individuals who have pertussis.

According to a new study in the journal Pediatrics, the most common cause of infection has changed. This new study found that immediate family members gave pertussis to infants in two-thirds of cases where the source of a baby’s infection could be identified. In other words, more than a third of babies caught pertussis from their brother, sister or grandparents. This study marks a departure from prior research, which found that moms are the most common person to give pertussis to their babies. The full article can be found here:

[Sources of Infant Pertussis Infection in
the United States](http://pediatrics.aappublications.org/content/early/2015/09/01/peds.2015-1120.full.pdf)

The study found that a brother or sister was the likely source of infection for 35.5% of the babies, followed by 21% who caught the disease from their mothers and 10% who caught it from their fathers. Grandparents accounted for 8% of the infections, and aunts and uncles account for 6.5%. The median age of siblings transmitting the illness was 8 years old, which is generally when the DTap vaccine becomes less effective.

While the authors of the study concluded that the best protection for newborn babies is still providing pregnant mothers with a vaccine booster during pregnancy, the study revealed a shift in the source of infant pertussis infections. The fact that the primary source of an infection can change is just one example of why it is so difficult to trace the origins of an infection, and by extension bring medical malpractice claims based upon acquisition of an infection.