No orders by the City of Fresno or County of Fresno in regard to the COVID-19 pandemic have as their subject matter parents' lawful visitation rights. Certain businesses have been ordered closed (https://www.fresno.gov/wp-content/uploads/2020/03/Businesses-Open-or-Closed-032020-7am.pdf). Certain other recommendations on containing the spread of the virus have been made. For the City of Fresno, see https://www.fresno.gov/coronavirus/ and for Fresno County see https://www.co.fresno.ca.us/departments/public-health/covid-19. Use your best judgment in deciding how to safeguard the health of you and your children during these times of heightened concern.

Yesterday, I reviewed the local Shelter in Place order in Santa Clara County, which is part of the SF Bay Area lock down so it is probably very similar to an order that might go into effect statewide or in Fresno County if a lock down is ordered. It specifically authorizes "Travel required by law enforcement or court order." Whether a court order regarding visitation exchanges is such a court order makes sense but there is no guidance yet as far as I know.
This leaves whether concerns about exposure to Coronavirus due to travel or to conditions at the place(s) the child will be with the other parent are grounds for denial or modification of visitation. Nobody knows how the courts and the legislature will ultimately handle this issue. This is just my take on what is likely. The current order remains in effect and there is no law explicitly overriding custody orders in the event of an Act of God or a government edict limiting travel or requiring Shelter in Place. However, given that the courts in many counties if not all over California are closed or only acting on emergency matters, it seems unlikely that a disgruntled parent will be able to enforce the custody order for the time being. Furthermore, it seems unlikely that a court would find a parent who in good faith based on verifiable facts decides to deny or modify visitation during a public health emergency to be in contempt of court. My advice is to try to work out a schedule of video conferencing or telephone calls between the absent parent and his or her children for the time being.