Rat Poison (Bromethalin-Based) in Dogs and Cats
Viral Diseases 101
Viral diseases are caused by viruses. They can impact many parts of your body, including your respiratory system, digestive tract, and skin.
Viral disease definition
Viruses are very small infectious agents. They're made up of a piece of genetic material, such as DNA or RNA, that's enclosed in a coat of protein.
Viruses invade cells in your body and use components of those cells to help them multiply. This process often damages or destroys infected cells.
A viral disease is any illness or health condition caused by a virus. Read on to learn more about some of the main types of viral diseases:
Not all viral diseases are contagious. This means they aren't always spread from person to person. But many of them are. Common examples of contagious viral diseases include the flu, the common cold, HIV, and herpes.
Other types of viral diseases spread through other means, such as the bite of an infected insect.
Respiratory viral diseases are contagious and commonly affect the upper or lower parts of your respiratory tract.
Common symptoms of a respiratory viral disease include:
Examples of respiratory diseases include:
TransmissionRespiratory viruses are spread by droplets generated through coughing or sneezing. If someone with a viral illness coughs or sneezes nearby and you inhale these droplets, you may develop the disease.
These viruses can also be spread through contaminated objects, such as doorknobs, tabletops, and personal items. If you touch one of these objects and then touch your nose or eyes, you could develop a disease.
TreatmentRespiratory viral diseases usually heal on their own. But over-the-counter (OTC) medications, including nasal decongestants, cough suppressants, and pain relievers, can help to reduce symptoms.
In addition, Tamiflu, an antiviral drug, is sometimes prescribed if someone is in the very early stages of developing the flu.
PreventionThe best way to avoid respiratory viral diseases is to practice good personal hygiene. Wash your hands often, cover your mouth when you cough or sneeze, and limit your interactions with people who show symptoms of a respiratory condition.
There's also a vaccine that can help to reduce your risk of getting the seasonal flu.
Gastrointestinal viral diseases affect your digestive tract. The viruses that cause them are contagious and usually lead to a condition called gastroenteritis, also called the stomach flu.
Common symptoms of gastrointestinal viral diseases include:
Examples of gastrointestinal viral diseases include:
TransmissionGastrointestinal viruses are shed in the stool during bowel movements. Food or water that's been contaminated by feces can spread the virus to others. You can also get the virus from sharing utensils or personal objects with someone who has a virus.
TreatmentThere aren't any treatments for gastrointestinal viral diseases. In many cases, they resolve on their own within a day or two. In the meantime, drink plenty of fluids to replace those lost from diarrhea or vomiting.
PreventionYou can prevent gastrointestinal viral diseases by washing your hands often, especially after using the bathroom. Wiping down contaminated surfaces and not sharing personal items or eating utensils can also help.
There's also a vaccine for rotavirus that's recommended as part of a child's vaccination schedule.
Exanthematous viruses cause skin rashes. Many of them cause additional symptoms as well.
Many of the viruses in this category, such as the measles virus, are highly contagious.
ExamplesExamples of exanthematous viral diseases include:
TransmissionMany exanthematous viruses are spread through respiratory droplets from the cough or sneeze of someone with the virus.
Other exanthematous viral diseases, such as chickenpox and smallpox, can be transmitted by coming into contact with fluid in broken skin lesions.
Shingles only occurs in people who've had chickenpox at some point. It's a reactivation of the varicella-zoster virus that's been lying dormant in your cells.
Chikungunya virus is spread through a mosquito bite and cannot be transmitted from person to person.
TreatmentTreating exanthematous viral diseases focuses on managing symptoms. Fever-reducing medications, such as acetaminophen, can help with some of the more bothersome symptoms.
Antiviral drugs, such as acyclovir, may be given for chickenpox or shingles.
PreventionMeasles, rubella, chickenpox, shingles, and smallpox can all be prevented through vaccination. You can reduce your risk of a chikungunya virus infection by protecting yourself from mosquito bites.
Learn more about viral rashes.
The hepatic viral diseases cause inflammation of the liver, known as viral hepatitis. The most common types of viral hepatitis are hepatitis A, B, and C.
It is worth noting that diseases caused by other viruses, such as cytomegalovirus and the yellow fever virus, can also affect the liver.
ExamplesExamples of hepatic viral diseases include:
Hepatitis B and C can be transmitted from person to person through bodily fluids. Sharing items that come in to contact with blood, such as needles or razors, can also spread the virus. Hepatitis B can be spread through sexual contact.
People get hepatitis A and E by consuming food or water that's been contaminated with feces from someone with the virus.
You can only develop hepatitis D if you already have the hepatitis B virus.
TreatmentTreatments for hepatitis B, C, and D focus on managing symptoms. In some cases, a doctor might prescribe medication, such as antiviral drugs.
Treatment of hepatitis A and E involves supportive measures, such as getting plenty of rest, drinking fluids, and avoiding alcohol.
PreventionThere are vaccines for both hepatitis A and hepatitis B. There's also a vaccine for hepatitis E, but it's not available in the U.S.
Other ways to prevent viral hepatitis include not sharing needles or razors, practicing safe sex, and avoiding food or drinks that may be contaminated by feces.
Cutaneous viral diseases cause lesions or papules to form on the skin. In many cases, these lesions can stick around for a long time or come back after disappearing for a while.
ExamplesExamples of cutaneous viral diseases include:
These viruses are contagious. They're usually spread through close physical contact with someone who has the virus or touching a contaminated object, such as a towel or faucet handle.
TreatmentPapules that form due to warts or molluscum contagiosum often go away on their own. They can also be removed by simple in-office procedures, such as cryotherapy.
There's no cure for herpes, but antiviral medications, such as acyclovir, can help to shorten or prevent outbreaks.
PreventionPracticing good hygiene habits, avoiding the sharing of personal items, and avoiding close contact with people who have active lesions can reduce your risk of developing a cutaneous viral disease.
Hemorrhagic viral diseases are severe conditions that involve damage to your circulatory system.
Symptoms of a hemorrhagic viral disease include:
Examples of viral hemorrhagic diseases include:
TransmissionSome hemorrhagic viral diseases, such as dengue fever and yellow fever, are spread through the bite of an infected insect.
Others, such as Ebola, are spread to other people through contact with the blood or other bodily fluid of someone with the virus. Lassa fever is spread through inhaling or consuming the dried feces or urine of a rodent with the virus.
TreatmentThere's no specific treatment for hemorrhagic viral diseases.
It's important to stay hydrated if you have a viral hemorrhagic disease. Some people may need intravenous (IV) fluids to maintain electrolyte balance. Supportive care to maintain hydration and electrolyte balance is essential. In some cases, the antiviral drug ribavirin may be given.
PreventionResearchers are in the process of developing vaccines for several hemorrhagic viruses. A yellow fever vaccine is currently available for people traveling to areas where yellow fever is common.
If you live or work in an area where viral hemorrhagic diseases are common, you can do the following to reduce your risk:
Some viruses can infect the brain and surrounding tissues, causing neurologic viral diseases. This can result in a range of symptoms, including:
Examples of neurologic viral diseases include:
Many neurologic viruses are spread through the bite of an infected animal or bug, such as a mosquito or tick.
Other viruses, such poliovirus and other enteroviruses, are quite contagious and spread through close contact with someone with the virus. Contaminated objects can also contribute to the spread of these viruses.
TreatmentThere's no specific treatment for people with mild viral meningitis or encephalitis. Getting plenty of rest, staying hydrated, and taking OTC anti-inflammatories to ease pain or headaches can all help. In some cases, antiviral medication may be prescribed.
Polio or severe cases of meningitis or encephalitis may require additional treatment, such as breathing assistance or IV fluids.
If an animal that's suspected to have the rabies virus bites you, you'll be given a series of shots to help prevent the rabies virus from infecting you.
PreventionThere's a vaccine for both poliovirus and the mumps virus, which can cause meningitis and encephalitis.
Practicing good hygiene, avoiding close contact with those who have the virus, and protecting against insect bites can all help to reduce the spread of encephalitis and meningitis.
To reduce the risk of spreading rabies, keep your pets vaccinated and avoid approaching wild animals.
There are many viral diseases. Some, such as the common cold or the stomach flu, are minor and go away on their own within a few days. Others, however, are more serious.
Unlike bacterial infections, viral diseases don't respond to antibiotics. Instead, treatment usually focuses on managing symptoms and supporting the immune system with plenty of rest and hydration.
Hepatitis D Virus-Like Agents Are Ubiquitous Throughout The Animal Kingdom
Photomontage of Animals
gettyThis story is part of a larger series on viroids and virusoids, small infectious RNAs. It is also the eighth installment in a series on hepatitis D virus, a virusoid-like pathogen that causes serious human disease. You may read the others on Forbes or www.Williamhaseltine.Com.
Hepatitis D virus has generally been considered an exclusively human pathogen, but a fast-growing body of research suggests otherwise. Hepatitis D virus-like agents seem to be active in a range of different animal species, from fish all the way to termites. Such findings call for a reevaluation of previous assumptions and a recognition that hepatitis D-like viruses may be significantly more pervasive than initially thought.
Hepatitis D "virus" is a tiny, infectious RNA pathogen. Far smaller than any known virus, it more closely resembles subviral agents known as viroids and virusoids. These are characterized by their circular genomes and lack of replication proteins: where viruses encode proteins to help them replicate their genetic information, viroids and virusoids instead hijack host-cell proteins. The same is true of hepatitis D virus. And like other virusoids, it is also understood to be dependent on the envelope proteins of a helper virus —in this case hepatitis B virus— for transmission between hosts and between cells.
Metatranscriptomics: Fishing for RNA Sequences
Central to these new findings is a technique called metatranscriptomics. Pioneered in the early 2000s, metatranscriptomics refers to a series of strategies that enable the characterization of the RNA content of large environmental samples. For example, researchers might extract a scoop of soil from a bog in Scotland and analyze that soil for all of the RNA sequences contained within it. The RNA can then be cross-referenced against large databases to establish matches with known RNA sequences
Metatranscriptomics allows researchers to extract massive amounts of RNA from environmental samples that would otherwise be difficult to study; in a sense, it acts as a giant sieve that filters out everything that isn't RNA content.
Duck, Duck, Hepatitis D?
One of the first traces of hepatitis D virus-like agents in non-human hosts was discovered in 2018 by a group of researchers based in Australia. As part of a broader avian metatranscriptome study, Wille et al. Analyzed throat and anal swabs collected from ducks caught at a water-treatment plant in Melbourne. They noticed that some of the RNA resembled that of human hepatitis D virus.
The nucleotide contents didn't quite match up — human hepatitis D virus has a guanine (G) and cytosine (C) content of 60%, whereas the guanine and cytosine content of the new sequences was only around 51%. This aside, the two RNA sequences shared many features suggestive of common ancestry. For one, the avian hepatitis D virus-like RNA was circular and folded in on itself to form an unbranched rod-like secondary structure, a key characteristic of human hepatitis D virus. The hepatitis D virus-like genome discovered in the duck samples also had an open reading frame with the capacity to express an 185-amino-acid-long protein. The location of this open reading frame within the genome very closely mirrors the location of the open reading frame seen in human hepatitis D virus (Figure 1). On top of this, certain sequences of the avian hepatitis D virus-like agents resemble those corresponding to the genomic and antigenomic ribozymes found in human hepatitis D virus. Indeed, both of these potential avian ribozymes had secondary structures very similar to those of human hepatitis D virus ribozymes (Figure 2).
Curiously, none of the duck samples showed any signs of infection with duck hepatitis B virus. One possible explanation for this is that non-human hepatitis D virus-like agents may take advantage of other viruses to make infectious particles and to transmit from cell to cell. This explanation is supported by later work, which showed that, even in humans, hepatitis B virus is not the only one that can function as a helper virus.
FIGURE 1. Location of genomic and antigenomic ribozyme sequences, and the predicted ORF of the delta ... [+] antigen in the avian HDV-like genome compared to their location in the HDV genome sequence.
SOURCE: ACCESS Health International (Adapted from: Wille et al. 2018 https://doi.Org/10.3390/v10120720)FIGURE 2. HDV ribozymes. (A) Secondary structures of the genomic and antigenomic ribozymes inferred ... [+] using the TT2NE algorithm. The HDV ribozyme models were used as reference to screen for the ribozyme sequences in the avian HDV-like genome sequence. (B) Re-drawn secondary structures of the genomic and antigenomic ribozymes.
SOURCE: Wille et al. 2018Not Just Ducks, Toads and Termites Too
Spurred on by these findings, Wille and colleagues revisited data collected during previous metatranscriptomic work, now with an eye towards identifying potential new hepatitis D virus-like agents. This earlier data included samples from amphibians, fish, reptiles, and invertebrates.
From the more than a billion nucleotides gathered across the various libraries, the researchers were able to isolate four novel hepatitis D virus-like agents. These belonged to Subterranean termite, Asiatic toad, Chinese fire belly newt, and a mixture of fish (Table 1).
TABLE 1. Characterization of the HDV-like agents and their putative HDAgs.
SOURCE: ACCESS Health International (Adapted from: Chang et al. 2019 https://doi.Org/10.1093/ve/vez021)As with the duck hepatitis D virus-like agents, the guanine/cytosine contents of these newly discovered varieties were also lower than in human hepatitis D virus. Still, all of the genomes were circular with unbranched rod-like secondary structures and their sizes consistent with other hepatitis D virus-like agents (1500-1700 nucleotides). Additionally, all of the newly discovered agents encoded a putative hepatitis D virus-like antigen protein, which, when cross-referenced against large protein databases, proved to be most closely related to the human delta antigen proteins. Even for the distinct domains within each of the putative antigen proteins, all of the "top scoring hits" matched human hepatitis D antigen protein.
Again, none of the data libraries contained any hepatitis B virus RNA. In fact, they didn't contain any hepadnavirus RNA of any kind. They did, however, contain sequences from other viruses which may have served a functionally similar role (Table 2).
TABLE 2. Details of the HDV-like agents and associated viruses discovered previously.
SOURCE: ACCESS Health International (Adapted from: Chang et al. 2019)This adds credence to the notion that hepatitis D virus and virus-like agents are not exclusively tethered to the hepatitis B virus and may instead be able to use other helper viruses to assist with transmission and infection.
Implications
Since the completion of these early studies, the list of potential hosts has been growing steadily. Aside from ducks, newts, toads and the rest of the abovementioned animals, hepatitis D virus-like agents have now also been found in white-tailed deer, passerine birds, and woodchucks. Clearly, the assumption that hepatitis D virus is a strictly human pathogen has reached its limit — the virus is far more widespread than initially thought. Not only this, but the range of helper viruses is also likely far more diverse than previously understood. None of the animal samples showed any indication of co-infection with hepatitis B virus, and yet hepatitis D virus persisted in great numbers. We have to begin acknowledging that hepatitis D virus-like agents likely adopt envelope proteins from a variety of sources. Different helper viruses may enable the infection of different tissues, and with this, cause diseases never previously associated with hepatitis D virus. We are only just beginning to scratch the surface.
Infected Mosquitos Could Bring Viruses Through Bites. How To Protect Yourself
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