Introduction
There are a few viruses that can spread from dogs to humans. One of the most notable is canine distemper virus (CDV). CDV is an enveloped, single-stranded RNA virus in the genus Morbillivirus. It is a highly contagious and life-threatening disease in dogs. While adult dogs may only experience mild symptoms, the virus can be fatal in puppies and unvaccinated dogs. CDV impacts a dog’s respiratory, gastrointestinal, and nervous systems (Ghasemzadeh, 2015).
Although CDV mainly infects dogs, it can also spread to people through close contact with an infected dog. However, human infections are rare. When transmission does occur, infected people may develop mild flu-like symptoms. There is no cure for CDV, but supportive care can help dogs and humans recover (KidsHealth).
Transmission
There are several viruses and bacteria that can be transmitted from dogs to humans. According to a review published in PLOS Neglected Tropical Diseases, the main route of transmission is through contact with a dog’s saliva and other bodily fluids (1). When a dog licks a person’s face or hands, contaminated saliva can enter through breaks in the skin or mucous membranes, allowing viruses and bacteria to spread.
Some common viruses transmitted this way include rabies, canine influenza, and canine herpesvirus. Bacterial infections like Capnocytophaga canimorsus and Pasteurella can also be spread through dog saliva. Other modes of disease transmission include contact with urine, feces, or respiratory secretions from an infected dog.
Sharing food and water bowls with dogs can enable disease transmission through saliva contact as well. Allowing dogs to lick open wounds or sores further increases risk. Puppies and dogs with poor health and weakened immune systems tend to shed more disease-causing germs, elevating transmission risk.
In summary, viruses and bacteria from dogs can spread to humans primarily through contact with saliva, especially by direct licking. Other bodily fluids may also transmit infectious diseases in some cases.
Symptoms
The most common dog virus that can spread to humans is canine influenza virus. The symptoms of this illness in dogs include cough, runny nose, fever, lethargy, eye discharge, and reduced appetite, but not all infected dogs will show signs of illness (CDC).
In humans, symptoms of canine influenza are generally similar to seasonal flu and can include fever, cough, sore throat, runny nose, headache, muscle aches, and fatigue. The illness usually resolves within 2 weeks. Severe illness is rare but more common in people with weakened immune systems. There are currently no vaccines available for canine influenza virus infections in humans (Ghasemzadeh et al., 2015).
Other dog viruses like rabies virus and hepatitis E virus can also spread to humans in rare cases. Rabies causes brain inflammation and can lead to symptoms like agitation, hallucinations, and hydrophobia. Hepatitis E can cause fever, nausea, vomiting, and jaundice.
Diagnosis
There are a few ways the dog virus can be diagnosed in humans. The most common diagnostic tests include:
- Blood tests to look for antibodies against the virus. A positive antibody test indicates past or current infection. (https://kidshealth.org/en/parents/pet-infections.html)
- Polymerase chain reaction (PCR) tests on blood, urine, or spinal fluid samples to detect the virus’s genetic material and confirm active infection.
- Culture tests that attempt to grow the virus from blood, urine, or spinal fluid samples.
- Imaging tests like X-rays, CT scans, and MRIs which can reveal abnormalities associated with the infection.
Diagnosis in humans often begins with recognizing the flu-like symptoms and confirming recent exposure to an infected dog. Diagnostic testing helps differentiate the dog virus from other infections with similar presentations. Timely, accurate diagnosis allows for appropriate treatment to improve outcomes.
Treatment
There is no direct treatment for canine parvovirus infection in dogs, so treatment focuses on supporting the body while it fights off the infection. This includes administering IV fluids to prevent dehydration, controlling vomiting and diarrhea, and providing supportive care such as nutritional supplementation. Antibiotics may be given to prevent or treat secondary bacterial infections. In severe cases, dogs may need to be hospitalized and given around-the-clock intensive care including blood plasma or whole blood transfusions. With aggressive treatment, the mortality rate is around 10-20% but can be higher in young puppies.
In humans, there is no specific treatment for parvovirus B19 infection. Supportive care includes over-the-counter medications to reduce fever and relieve joint pain and swelling. In people with chronic anemia or immune system problems, intravenous immunoglobulin (IVIG) containing antibodies can raise blood cell counts. For severe fetal infections, blood transfusions can be given in utero. Overall the prognosis is good, although the infection can be serious or even fatal in people with blood disorders or weakened immune systems.
Prevention
There are several ways to help prevent the spread of zoonotic diseases between dogs and humans:
Vaccinate dogs – Keeping dogs up to date on core vaccines like rabies, distemper, parvo and adenovirus can help prevent transmission of these viruses. According to the CDC, rabies kills 59,000 people worldwide each year, so rabies vaccination is critical.
Deworm dogs regularly – Intestinal parasites like roundworms and hookworms can spread from dogs to humans, especially children. Regular deworming helps remove worm larvae that shed in the feces.
Avoid contact with dog feces – Proper disposal and cleanup of dog feces prevents spread of bacteria, viruses and parasites. Always wash hands after handling dog waste.
Practice good hygiene – Washing hands frequently, avoiding kissing or being licked by dogs near the mouth and face, and not allowing dogs to lick open wounds helps prevent spread of diseases.
Control ticks, fleas and mosquitos – These insects can transmit diseases between species. Use preventives on pets and check regularly for attachments.
Know your dog’s health – Monitor for signs of illness and keep sick pets away from other animals and people. Seek veterinary care for concerning symptoms. Don’t expose immunocompromised individuals to pets.
Avoid contact with wild animals – Wild animals like raccoons and bats can harbor rabies and other viruses transmissible to dogs. Keep pets away from wildlife and do not touch or feed wild animals.
Outbreak History
Canine influenza virus (CIV) was first detected in racing greyhounds in Florida in 2004. This strain, known as H3N8, is closely related to an equine influenza virus. It likely jumped species from horses to dogs. The H3N8 CIV spread to many states and caused outbreaks in shelters and kennels. Vaccines were developed to help prevent spread of this virus.
In 2015, a new strain of CIV emerged in the United States. This H3N2 strain originated in Asia and was first detected in dogs in Chicago. It rapidly spread nationwide, causing outbreaks in many shelters, pet stores, boarding facilities, dog parks, and other sites where dogs congregate. The virus spread very quickly since most dogs had no immunity to this new strain. [1]
Both H3N8 and H3N2 continue to cause sporadic outbreaks in the US. H3N2 has become endemic in the dog population. Shelters and boarding kennels are especially vulnerable due to the frequent mixing of dogs from various sources. [2]
Current Status
As of January 2023, the mysterious dog illness has been reported in over 16 states across the U.S. The most recent outbreaks seem to be concentrated on the West Coast, with over 100 cases reported in Southern California, including Los Angeles and San Diego counties (https://www.cbsnews.com/news/dogs-respiratory-illness-map-acirdc/). In the San Francisco Bay Area, there have been confirmed cases in San Francisco, Alameda, Contra Costa, San Mateo, Santa Clara, Solano and Sonoma counties. Veterinarians are also reporting cases in Washington state, Idaho, Texas, New Mexico and Michigan.
The illness was first detected in dogs in August 2022, but has spread rapidly over the past few months. The current outbreaks on the West Coast are the largest and most severe so far. Experts believe the disease is highly contagious based on the rapid increases in cases when it enters a new area. However, the exact origin and mode of transmission remains unknown.
Research
Researchers are working to identify the cause and spread of this concerning canine illness. According to Dr. Scott Weese, an infectious disease veterinarian at the Ontario Veterinary College, the current outbreak seems to be a “new presentation of disease with a new clinical syndrome in dogs” (NPR). Much is still unknown about the viral culprit, but samples from affected dogs are being analyzed in laboratories across the country.
Cornell University and the New York State Animal Health Diagnostic Center have been sequencing samples and comparing results to known pathogens, but have yet to find a clear causative agent. Researchers at the University of Georgia Veterinary Diagnostic Laboratories have also been investigating samples, looking for both known and novel viruses that could be responsible (NBC News).
While the research continues, infectious disease experts recommend observing good hygiene practices like washing hands after handling dogs to limit any potential human transmission until more details are known.
Conclusion
Overall, there is a canine virus known as canine influenza that in rare cases can spread from dogs to humans. However, human infections tend to be mild and limited. The main way humans can get infected is through close contact with dogs that are ill with canine influenza. The best way to prevent transmission is by vaccinating dogs against canine flu viruses. While outbreaks have occurred, they have remained fairly limited in scope. With proper precautions and awareness, the risk of humans contracting canine influenza is low. In summary, canine influenza very rarely jumps species but virologists continue researching transmission patterns to further reduce risks of contagion.