Health authorities in the United States are issuing warnings and closing public parks because of a rare but potentially deadly mosquito-borne disease.
This week, a resident of the US state of New Hampshire he died after being hospitalized for Eastern encephalomyelitis. Cases have also been detected in other states.
But what is eastern equine encephalitis? How does it spread? What do horses, as the name suggests, need to do with it? And is it an issue for Australia?
What is Eastern Encephalomyelitis?
Eastern encephalomyelitis It is attributable to a virus that is often found only in parts of eastern America, Central America Down Canada.
Eastern encephalomyelitis virus causes neurological disease, specifically encephalitis (inflammation and swelling of the brain), and is transmitted to humans by mosquito bite. Symptoms might be serious and potentially fatal.
But most individuals bitten by a mosquito carrying the virus won’t have symptoms. Those who do develop the disease have symptoms that include headache, stiff neck, disorientation, seizures, and coma.
About one third Patients with severe symptoms die, and lots of of those that survive suffer from chronic neurological problems.
It’s not only humans who’re in danger from the virus. Horses are too susceptible and, like humans, they may contract deadly encephalitis when bitten by an infected mosquito.
The virus was discovered after the outbreak of the epidemic fatal disease in horses in the New England region of the USA in 1831, hence the reference to a horse disease in the name.
Wild, farmed and captive birds can even be infected with the virus and a few species develop disease. In fact, birds are key to how the virus spreads.
How is Eastern encephalomyelitis virus spread?
Birds – especially passerinea gaggle that features robins, starlings, thrushes and blue jays – are the predominant hosts of the virus.
These birds produce high enough levels of the virus that allow it to contaminate biting mosquitoes and maintain what is called the “transmission cycle.”
Mosquitoes feeding on birds in forested wetlands, especially , allow the virus to flow into amongst the birds. However, this mosquito rarely bites humans, so it is not as necessary in human disease outbreaks.
Mosquitoes feed on each birds and mammals that transmit the virus to humans and horses. These include , and mosquitoes. But once infected, humans and horses don’t spread the virus. This is because they don’t produce high enough levels of the virus to contaminate mosquitoes.
A/Prof Cameron Webb (Health Pathology NSW)
How can we limit the spread?
There aren’t any specific treatments for Eastern encephalomyelitis virus infection, or any licensed vaccines to be used in humans. There is a vaccine registered for veterinary use to forestall viral infections in horses.
The predominant strategies to limit human exposure to the virus are personal protective equipment and mosquito control.
Epidemics can have a major impact on communities, not only due to the disease itself, but in addition due to the measures implemented to limit its transmission.
Recent outbreaks have led to the cancellation of out of doors events. Concerns have also been raised about the widespread use of aerial “fogging” to kill mosquitoes, as the chemicals commonly used should not specific to mosquitoes and should pose a risk to other insects.
Some cities have closed park areas evening and asked residents not to depart their homes at night.
Why did the epidemic break out now?
The virus circulates throughout the 12 months in tropical regions. like FloridaIn the northeastern a part of the USA the virus has more sporadic activityHere it is often introduced by migratory birds and is energetic during the warmer months when the mosquito population is high.
This virus has been known for a lot of a long time and has had many outbreaks in North America. One of the last major outbreaks It was in 2019 in several northeastern states of the USA, when 38 human cases (including 12 deaths).
There is evidence that the virus is spreading to latest regions of North America. However, given the sporadic nature of the epidemic, it is difficult to predict when it would occur.
Many aspects could influence future disease outbreaks and the spread of the virus to latest regions, including climate, environmental aspects, mosquito and wildlife activity, and, importantly, humans.
As human contact with mosquitoes that may carry the virus from infected birds increases, the risk to public health increases.
It is possible that human activity near mosquito and bird habitats, including urban encroachment on forested wetlands, increases the risk.
That is why it is so necessary for health services to watch mosquito and virus activity. provide early warning risk of human disease.
Jeff Holcombe/Shutterstock
Is there a risk to Australia?
There is no evidence that eastern encephalomyelitis virus occurs in Australia and there is no immediate risk of its introduction into this country.
While the mosquitoes are situated in AustraliaTheir role in local viral epidemics in humans and animals is not well understood.
But dozens of various mosquitoes are involved on this process. spread of alphaviruses in Australia. This group includes the eastern encephalomyelitis viruses, in addition to those who occur in Australia, namely Ross River AND Barmah Forest viruses.
It might be assumed that a few of these mosquitoes can transmit the virus, but this has not yet been tested in laboratory experiments.
There is little or no information on how local passerine birds may play a task in establishing virus transmission cycles in Australia. There is also no information on whether native Australian vertebrates, reminiscent of marsupials, would reply to infection.
Considering all available evidence, the risk of the virus spreading to Australia and causing an epidemic is most probably very low.
Are travellers in danger?
The risk of being bitten by a mosquito carrying eastern encephalomyelitis virus is extremely low. However, anyone visiting eastern regions of North America, including the United States and Canada, where the virus could also be present, should take precautions to avoid being bitten by mosquitoes.
Follow guidance from local health authorities. And take steps to avoid areas (especially wooded wetlands) and times when mosquitoes are energetic (often at dawn and dusk). Wear loose clothing with long sleeves and use repellents containing diethyltoluamide (commonly often called DEET), picaridin, or oil of lemon eucalyptus.
These precautions may even protect you from contracting other mosquito-borne viruses you may encounter there, reminiscent of: West Nile Virus.