How is giardiasis USUALLY transmitted to others?

Transmission of giardiasis, a gastrointestinal illness caused by the parasite Giardia lamblia, primarily occurs through the fecal-oral route. The most common way this happens is through the transfer of cysts present in the feces of an infected individual. This can occur when a person comes into direct contact with the stool of an infected person or indirectly through contamination of surfaces or food.

In crowded settings or where personal hygiene is lacking, such as daycares or among family members, the transmission via person-to-person contact becomes more prevalent. Therefore, the option highlighting the direct transfer of cysts from the feces of an infected individual effectively captures the primary and usual transmission mechanism for giardiasis, emphasizing the importance of sanitation and personal hygiene in preventing its spread.