Parvo Is Back With a Vengeance: Why Falling Vaccine Rates Are Turning Clinics Into Crisis Zones

Late last month, veterinary clinics across the Phoenix metro area began sounding the alarm. Canine parvovirus cases surged far beyond seasonal expectations, overwhelming hospitals that were already stretched thin. One clinic treated 47 parvo cases in November alone, roughly five times its typical monthly volume. Another Phoenix hospital told local station 12 News it had seen hundreds of infected dogs and described the situation bluntly as an emergency. For many veterinarians, the surge feels like a flashback to a disease era we thought we had mostly beaten.

Why parvo is surging now

Parvo is nothing new, but the conditions fueling its return are deeply familiar. According to Dr. Thomas Satkus, record rainfall may be helping the virus persist in soil, puddles, and communal areas where dogs congregate. Canine parvovirus is notoriously resilient in the environment, capable of surviving for months under the right conditions. But weather alone does not explain the scale of the outbreak.

Lower vaccination rates appear to be the real accelerant. Clinics report more unvaccinated and partially vaccinated puppies than they have seen in years, creating ideal conditions for explosive spread. Parvo remains one of the most dangerous infectious diseases veterinarians treat. It attacks rapidly dividing cells in the gastrointestinal tract and bone marrow, leading to severe vomiting, hemorrhagic diarrhea, dehydration, sepsis, and death. Without treatment, mortality rates can exceed 90 percent. Even with aggressive hospitalization, care is intensive, costly, and emotionally exhausting for staff and clients alike.

Arizona is not alone. Last winter, San Francisco neighborhoods saw parvo infection rates double in some areas, according to the local SPCA. Meanwhile, distemper outbreaks have emerged in California’s Central Valley and Los Angeles County, forcing shelters into crisis mode. In August, Madera County Animal Services temporarily closed due to distemper. In October, nearly 200 dogs were euthanized at a Los Angeles County shelter after an outbreak traced back to community transmission in eastern Lancaster.

Both parvo and distemper are core vaccine preventable diseases. Both are covered by the DAPP vaccine that veterinarians routinely recommend for every dog. Dr. Jane E. Sykes, professor of veterinary medicine at UC Davis, emphasizes that vaccination remains highly effective. Distemper, in particular, continues to be one of the most devastating shelter diseases due to its high mortality and neurological complications.

Distemper belongs to the same viral family as measles, a comparison that feels uncomfortably relevant. The United States declared measles eliminated in 2000, yet declining human vaccination rates have allowed cases to climb to their highest levels in decades. Dr. Sykes warns that the same pattern can unfold in pet populations.

When vaccination rates drop below protective thresholds, diseases that once seemed rare reappear quickly. Owned dogs are not immune to this trend, especially when misinformation spreads faster than medical guidance. The stakes extend beyond animal health. Diseases like leptospirosis and rabies pose direct zoonotic risks. As Dr. Steve Weinrauch, chief veterinary officer at Trupanion, has noted, modern pets are more integrated into human households than ever. Dogs sleep in beds, lick faces, and interact closely with children. The barrier between animal and human health is thinner than many owners realize.

Veterinary professionals are on the front lines of this resurgence, and client education has never been more critical.

Vaccination remains the cornerstone. Puppies should begin the DAPP series at 6 to 8 weeks with appropriately timed boosters. Adult dogs require routine boosters to maintain immunity, especially in high risk regions.

Early recognition saves lives.
Parvo signs include vomiting, bloody diarrhea, lethargy, anorexia, and rapid dehydration.
Distemper may present with coughing, fever, ocular or nasal discharge, gastrointestinal signs, seizures, or muscle twitching.

Risk mitigation matters during outbreaks. Advise clients to avoid dog parks, daycare, boarding facilities, and group play when local cases rise, particularly for young or incompletely vaccinated dogs.

Environmental control is essential. Parvo is resistant to most disinfectants. Bleach based solutions remain among the few reliably effective options for contaminated surfaces.

Prompt intervention is nonnegotiable. Both parvo and distemper progress rapidly. Early hospitalization significantly improves survival and reduces suffering.

What this means for vets

From a client perspective, parvo treatment routinely costs hundreds to thousands of dollars, far exceeding the price of preventive vaccines. For shelters and municipalities, outbreaks strain already limited resources and increase euthanasia risk. For veterinary teams, these cases contribute to compassion fatigue and burnout. Preventable disease feels especially heavy when outcomes could have been avoided.

The current parvo surge is more than a regional headline. It is a warning signal. Declining vaccination rates do not just bring back old diseases. They test the resilience of veterinary systems, shelters, and public trust. Vaccination remains one of the most powerful tools veterinarians have to protect pets, safeguard communities, and prevent crises before they start.