Discovered in mosquitoes in the Barmah Forest in northern Victoria in Australia in 1974, Barmah Forest Virus was simultaneously found in mosquitoes trapped in southwest Queensland. Previous to 1974, this virus had never been identified. Barmah Forest Virus went unmeasured in humans until 1986, when it was detected at New South Wales. The first indication that it caused discernible disease finally occurred in 1988.
In 1989, the virus jumped to western Australia mosquitoes, 3,000 kilometers away. A few cases developed in the same locale in 1992, with a substantial outbreak a year later.
By 2009, Barmah Forest virus had spread to other areas within Australia, and an intermediate host--an animal between the mosquito and the human--is suspected: the marsupial, perhaps the widespread opossum.
Significance
Recognizing Barmah Forest Virus (BFV) is complicated because its symptoms resemble the more well-known Ross River Virus, which is the most common mosquito-spread viral illness in Australia. Only blood work can distinguish the two infections. In spite of their similarities, Barmah Forest Virus remains far rarer, and has less severe extended symptoms. While Ross River Virus has jumped to many countries, BFV has, for now, been contained to Australia.
Symptoms
Symptoms begin anywhere from three to 21 days after infection, most commonly within seven to nine days after being bitten by an infected mosquito. While one-third of children may have subclinical (unapparent) infection, and an equal number of adults are likewise spared, those impacted will sometimes feel quite ill, though all will eventually recover.
The first complaints are flu-like symptoms of fever, chills, nausea, loss of appetite, sore throat, night sweats, joint pain, muscle aches, malaise, fatigue and headaches.
Unlike the flu, both Barmah Forest viral (BFV) and Ross River (RR) infections often have early rash and joint swelling. The rash is more dramatic in Barmah Forest Virus, with a ruddier, measles-like eruption that can even blister. The rash begins with small red dots on the extremities (sometimes including palms and soles) and the trunk and abdomen.
Both viral entities often have multiple, severe, painful joint swelling, which can on rare occasions be disabling for up to two or more years, especially the Ross River Virus. However, while BFV usually runs its course in a few weeks, some cases of Barmah Forest Virus have also taken as long as two years to clear up. For both viruses, the affected joints tend to be symmetrical: wrists, hands, knees, ankles and feet. Least likely to be involved are the jaw, hips and spine.
The only good news, even in such prolonged disability, is that joints so involved are NOT permanently disfigured or damaged and full recovery is likely.
Diagnosis
Since Australia has several arboviruses (viruses spread by mosquitoes) that can look similar, the best way to diagnose BFV is to draw antibody titers 10 days apart to see if there has been a rise in immunity.
Treatment
There is no specific cure. In other words, no way exists to head off the disease once you have likely been bitten or develop symptoms. Treatment is supportive, which means adequate rest, good nutrition, Tylenol or other non-steroidal medicines as needed for pain, and a hopeful outlook for a quick and full recovery. If painful, temporary disability does occur, then all the above still holds true as well as gentle exercise and supportive emotional care. Once diagnosed, a person is probably immune for life.
Prevention advice: Visiting Australia safely includes wearing light mosquito-protective clothing; avoid being outside in early evening in the warm summer months; wear and replenish mosquito repellent frequently; and sleep in screened-in quarters.
