Diseases caused by viruses Questions in English

(A) The rabies virus,which belongs to the genus $Lyssavirus$ and family $Rhabdoviridae$,contains a single-stranded $RNA$ genome. This $RNA$ is negative-sense and non-segmented.

(B) The influenza virus belongs to the family $Orthomyxoviridae$.
It is an enveloped virus,meaning its nucleocapsid is surrounded by a lipid bilayer membrane derived from the host cell.
This envelope contains viral glycoproteins such as hemagglutinin $(HA)$ and neuraminidase $(NA)$,which are essential for viral attachment and entry into host cells.
Therefore,the influenza virus possesses an enveloped capsid.

(C) Arthropod-borne viruses are commonly referred to as $Arbo$ viruses.
These viruses are transmitted to humans and other vertebrates by arthropod vectors such as mosquitoes,ticks,and sandflies.
The term '$Arbo$' is an abbreviation derived from '$Ar$'thropod-'$bo$'rne.

(A) Vertical transmission refers to the passage of a pathogen from mother to child during the period immediately before and after birth.
This can occur via the placenta during pregnancy,through the birth canal during delivery,or via breast milk.
Therefore,the placenta of the mother is a primary route for vertical transmission of viruses such as $HIV$,Rubella,or Cytomegalovirus.

(D) is the correct answer.
$Encephalitis$ virus is responsible for causing inflammation of the brain,specifically targeting the gray matter.
This condition is clinically referred to as $Encephalitis$,which often presents as brain fever,leading to symptoms like headache,fever,and confusion.

(C) Hydrophobia,commonly known as rabies,is a viral disease.
It is caused by the rabies virus,which belongs to the family $Rhabdoviridae$.
The virus is typically transmitted to humans through the saliva of infected animals,usually via a bite.
Therefore,the correct option is $C$.

(A) The correct answer is $A$.
$1$. Potato mosaic is a viral disease caused by the Potato Virus $Y$ $(PVY)$ or Potato Virus $X$ $(PVX)$.
$2$. Citrus canker is a bacterial disease caused by $Xanthomonas$ $axonopodis$ $pv.$ $citri$.
$3$. Brown rot of potato is caused by the bacterium $Ralstonia$ $solanacearum$.
$4$. Leaf spot of cotton is typically caused by fungi such as $Alternaria$ $macrospora$.

(B) Interferons are a group of signaling proteins made and released by host cells in response to the presence of several pathogens,such as viruses,bacteria,parasites,and tumor cells.
In $1957$,Alick Isaacs and Jean Lindemann discovered that proteins synthesized by human cells during viral infections provide immunity against the same or other viruses. These proteins are known as interferons. They act as cytokines that inhibit viral replication within host cells.

(C) The term 'mosaic' refers to a pattern of disease symptoms in plants where patches of chlorosis (yellowing due to loss of chlorophyll) are interspersed with normal green tissue. This pattern is a characteristic symptom of many plant viral infections,such as the Tobacco Mosaic Virus $(TMV)$.

(A) viral disease is caused by a virus.
$A$. Smallpox is caused by the Variola virus,and polio is caused by the Poliovirus.
$B$. Malaria is caused by a protozoan parasite,Plasmodium.
$C$. Diphtheria is caused by the bacterium Corynebacterium diphtheriae.
$D$. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
Therefore,smallpox and polio are viral diseases.

(A) Mumps is an acute viral infection caused by the mumps virus,which belongs to the family $Paramyxoviridae$.
It primarily affects the parotid glands,which are major salivary glands located below and in front of the ears.
Since it is caused by a virus,it is classified as a viral disease.

(B) The common cold is a viral infectious disease of the upper respiratory tract.
It is primarily caused by rhinoviruses,which belong to the family $Picornaviridae$.
These viruses infect the lining of the nose,throat,and sinuses,leading to symptoms such as sneezing,sore throat,and nasal congestion.

(A) Yellow fever is an acute viral hemorrhagic disease caused by the yellow fever virus.
It is transmitted to humans by the bite of infected mosquitoes,primarily of the $Aedes$ genus.
Therefore,the correct cause is a virus.

(D) pandemic is an epidemic of an infectious disease that has spread across a large region,for instance multiple continents or worldwide. Influenza is caused by the influenza virus and has historically caused several global pandemics (e.g.,the $1918$ Spanish flu). Amoebic dysentery,hepatitis,and filariasis are generally endemic or epidemic in nature but do not typically reach pandemic status.

(B) Influenza is caused by a virus,specifically the Influenza virus.
It is an $RNA$ virus characterized by a helical capsid surrounded by an envelope containing surface spikes (hemagglutinin and neuraminidase).
Therefore,the correct option is $B$.

(D) $Aedes$ mosquitoes are well-known vectors for several viral diseases.
Specifically,$Aedes$ $aegypti$ and $Aedes$ $albopictus$ are the primary vectors for the transmission of $Dengue$ virus.
Additionally,$Aedes$ mosquitoes can also transmit other arboviruses such as $Chikungunya$,$Zika$,and certain forms of $Encephalitis$ (like $Japanese$ $Encephalitis$ is primarily $Culex$,but $Aedes$ is associated with others).
Among the given options,$Dengue$ is the most accurate association for $Aedes$.

(B) The correct answer is $B$. Poliomyelitis,commonly known as polio,is a highly infectious viral disease caused by the poliovirus. It affects the nervous system and can lead to muscle weakness,paralysis,and atrophy of the affected muscles due to the destruction of motor neurons in the spinal cord.

(A) The aphid $Acyrthosiphon$ $pisum$ is a well-known vector for the transmission of the Pea mosaic virus.
This virus causes the Pea mosaic disease in leguminous plants.
Therefore,the correct option is $A$.

(B) $1.$ Burkitt's lymphoma is a cancer of the lymphatic system, specifically $B$-cells, and is strongly associated with the Epstein-Barr virus $(EBV)$.
$2.$ Adult $T-$cell leukemia is a rare type of cancer of the $T-$cells (a type of white blood cell) caused by the Human $T-$lymphotropic virus type $1$ $(HTLV-1)$.
$3.$ Phenylketonuria $(PKU)$ is an inherited metabolic disorder caused by a genetic mutation in the $PAH$ gene, not by a virus.
Therefore, only $1$ and $2$ are caused by viruses.

(B) $KFD$ virus,which causes Kyasanur Forest Disease,is a tick-borne flavivirus.
It is considered a dual host virus because it cycles between its primary vector (ticks,such as $Haemaphysalis$ $spinigera$) and various vertebrate hosts,including small mammals,monkeys,and humans.

(B) $SARS$ stands for Severe Acute Respiratory Syndrome.
It is a viral respiratory disease caused by the $SARS-associated$ coronavirus $(SARS-CoV)$,which is a member of the coronavirus family,the same family that includes viruses responsible for the common cold.
It is characterized by high fever,headache,and respiratory symptoms like cough and shortness of breath.

(C) Interferons are antiviral proteins produced by virus-infected cells to protect non-infected cells from further viral infection.
Among the given options,$Typhoid$,$Malaria$,and $Tetanus$ are caused by bacteria or protozoa.
$Measles$ is a viral disease caused by the $Measles$ virus.
Therefore,the production of interferon is most likely associated with a viral infection like $Measles$.

(A) Hydrophobia,commonly known as rabies,is an acute and typically fatal infectious disease caused by a virus that affects the central nervous system of mammals.
Human infection primarily occurs through the bite of an infected animal,such as a dog,bat,or other rabid mammals.

(C) communicable disease is an infectious disease that can be transmitted from one person to another or from an animal to a human.
$1$. $Phenylketonuria$ and $Alkaptonuria$ are genetic (inborn errors of metabolism) disorders,which are non-communicable.
$2$. $Cancer$ is a non-communicable disease caused by uncontrolled cell division.
$3$. $Rabies$ is a viral disease transmitted to humans through the bite of an infected animal (usually dogs),making it a communicable (infectious) disease.

(C) Dengue fever is a viral disease caused by the dengue virus.
It is transmitted to humans primarily through the bite of infected female mosquitoes of the genus $Aedes$, specifically $Aedes$ $aegypti$.
$Anopheles$ mosquitoes are vectors for malaria, $Culex$ mosquitoes can transmit diseases like filariasis and Japanese encephalitis, and $Musca$ (housefly) is a mechanical carrier of various pathogens.

(A) Smallpox is a highly contagious and serious infectious disease caused by the $Variola$ virus.
It belongs to the genus $Orthopoxvirus$.
The virus spreads primarily through direct contact with infected individuals or contaminated materials.
Therefore,the correct causative agent is a virus.

(B) Polio,also known as poliomyelitis,is a highly infectious disease caused by the poliovirus.
The poliovirus belongs to the genus $Enterovirus$ in the family $Picornaviridae$.
Structurally,the poliovirus is a non-enveloped virus that contains a single-stranded $RNA$ genome of positive polarity.
Therefore,the correct option is $B$.

(B) viral disease is caused by a virus.
$A$. Syphilis is a bacterial disease caused by the bacterium $Treponema \text{ } pallidum$.
$B$. Measles is a viral disease caused by the measles virus (a member of the $Paramyxoviridae$ family).
$C$. Rickets is a nutritional disorder caused by a deficiency of Vitamin $D$.
$D$. Beri-beri is a nutritional disorder caused by a deficiency of Vitamin $B_1$ (thiamine).
Therefore, the correct option is $B$.

(B) Jaundice is a condition characterized by the yellowing of the skin and eyes due to high levels of bilirubin in the blood.
In the context of infectious diseases,Hepatitis (specifically Hepatitis $A$,$B$,$C$,$D$,and $E$) is the most common viral cause of jaundice.
Since Hepatitis is caused by a virus,the correct answer is $B$.

(D) Tetanus is caused by the bacterium $Clostridium \text{ tetani}$.
Dysentery is primarily caused by protozoans like $Entamoeba \text{ histolytica}$ or bacteria like $Shigella$.
Typhoid is caused by the bacterium $Salmonella \text{ typhi}$.
Since none of the options listed are viral diseases, the correct answer is $D$.

(B) Chicken pox is a highly contagious viral infection caused by the $Varicella-zoster$ virus $(VZV)$.
It is characterized by an itchy,blister-like rash on the skin.
The virus spreads easily through respiratory droplets or direct contact with the fluid from the blisters.

(B) The correct answer is $B$ (Influenza).
$1$. Influenza is a viral infection caused by the influenza virus.
$2$. Malaria is caused by a protozoan parasite of the genus $Plasmodium$.
$3$. Diphtheria is a bacterial infection caused by $Corynebacterium$ \text{ diphtheriae}.
$4$. Typhoid is a bacterial infection caused by $Salmonella$ \text{ typhi}.

(C) Dengue fever is a viral disease caused by the $Dengue$ virus $(DENV)$.
It is transmitted to humans through the bite of an infected $Aedes$ $aegypti$ mosquito.
Since it is caused by a virus,option $C$ is the correct answer.

(B) Japanese Encephalitis is a viral disease caused by the Japanese Encephalitis virus $(JEV)$.
It is primarily transmitted to humans through the bite of infected mosquitoes belonging to the genus $Culex$, specifically $Culex \text{ tritaeniorhynchus}$.
These mosquitoes typically breed in rice paddies and stagnant water bodies, making rural areas more prone to the disease.

(B) Small pox is a viral disease caused by the Variola virus.
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
Cholera is caused by the bacterium Vibrio cholerae.
Typhoid is caused by the bacterium Salmonella typhi.
Therefore, the correct option is $B$.

(A) Yellow fever is a viral disease caused by the yellow fever virus,which is transmitted to humans through the bite of infected mosquitoes.
Typhoid is caused by the bacterium $Salmonella$ $typhi$.
Syphilis is caused by the bacterium $Treponema$ $pallidum$.
Tetanus is caused by the bacterium $Clostridium$ $tetani$.
Therefore,the correct option is $A$.

(D) The smallest known human virus is the Poliovirus,which belongs to the genus $Enterovirus$ and the family $Picornaviridae$. It is approximately $30 \ nm$ in diameter. This virus is the causative agent of $Poliomyelitis$ (polio). Therefore,among the given options,$Poliomyelitis$ is caused by the smallest virus.

(B) Measles is a highly contagious viral disease caused by the measles virus.
Common symptoms include a high fever,cough,runny nose (coryza),and red,watery eyes (conjunctivitis).
As the disease progresses,a characteristic rash appears,which typically starts on the face and spreads downwards to the rest of the body.
This rash consists of small,red spots.
Therefore,the eruption of small red spots and the inflammation of the mucous membranes of the nose are classic clinical features of measles.

(B) The polio virus is an enterovirus,which primarily enters the body through the fecal-oral route.
Upon ingestion,the virus first multiplies in the cells of the gastrointestinal tract,specifically the intestinal cells (epithelial cells of the gut) and lymphoid tissues (like Peyer's patches).
From the intestine,it can spread to the bloodstream and eventually reach the central nervous system,where it may infect and destroy motor neurons,but its primary site of initial multiplication is the intestinal tract.

(A) Mumps is an acute viral infection caused by the mumps virus,which belongs to the family $Paramyxoviridae$.
It primarily affects the parotid glands,which are major salivary glands located below and in front of the ears.
Since it is caused by a virus,it is classified as a viral disease.

(D) viral disease is caused by a virus.
$1$. Tetanus and typhoid are caused by bacteria ($Clostridium tetani$ and $Salmonella typhi$ respectively).
$2$. Syphilis is caused by a bacterium ($Treponema pallidum$), while $AIDS$ is caused by a virus ($HIV$).
$3$. Whooping cough is caused by a bacterium ($Bordetella pertussis$), and sleeping sickness is caused by a protozoan ($Trypanosoma brucei$).
$4$. Measles is caused by the Measles virus, and rabies is caused by the Rabies virus ($Lyssavirus$).
Therefore, both diseases in option $D$ are viral.

(A) Yellow fever is a viral disease caused by the yellow fever virus.
It is transmitted to humans primarily through the bite of infected mosquitoes,specifically the $Aedes$ $aegypti$ species.
Therefore,the mosquito acts as the vector or carrier for this virus.

(B) Interferons are antiviral proteins produced by virus-infected cells to protect non-infected cells from further viral infection.
Among the given options, $Typhoid$ is caused by a bacterium $(Salmonella \text{ } typhi)$, $Tetanus$ is caused by a bacterium $(Clostridium \text{ } tetani)$, and $Malaria$ is caused by a protozoan $(Plasmodium \text{ } species)$.
$Measles$ is a viral disease caused by the $Rubeola \text{ } virus$.
Therefore, the production of interferons indicates a viral infection, making $Measles$ the correct answer.

(C) Smallpox is an acute,highly communicable disease caused by the $Variola$ virus.
It has been officially declared eradicated from India and the world through global vaccination programs.
While other diseases like polio have been eliminated from India,smallpox is the classic example of a disease that has been completely eradicated globally.

(D) Dengue is a viral disease caused by the dengue virus $(DENV)$.
It is primarily transmitted to humans through the bite of infected female mosquitoes, most notably $Aedes$ $aegypti$ and sometimes $Aedes$ $albopictus$.
These mosquitoes typically bite during the day.
$Culex$ mosquitoes are generally associated with the transmission of diseases like Japanese encephalitis and filariasis, while $Anopheles$ mosquitoes are vectors for malaria.
The $Tse-tse$ fly is the vector for African sleeping sickness.

(C) Foot-and-mouth disease is a highly contagious viral disease that affects cloven-hoofed animals,including cattle,sheep,and pigs.
It is caused by the Foot-and-mouth disease virus $(FMDV)$,which belongs to the genus $Aphthovirus$ in the family $Picornaviridae$.
Therefore,the correct option is $C$.

(D) The correct answer is $D$.
$1$. Plague is a bacterial disease caused by $Yersinia pestis$.
$2$. Cholera is a bacterial disease caused by $Vibrio cholerae$.
$3$. Asthma is a chronic respiratory condition, often allergic in nature, not caused by a virus.
$4$. Polio (Poliomyelitis) is a highly infectious viral disease caused by the poliovirus, which affects the nervous system.

(B) Retroviruses are a group of viruses that possess $RNA$ as their genetic material. Upon entering a host cell,they use the enzyme reverse transcriptase to transcribe their $RNA$ into $DNA$,which then integrates into the host genome. Therefore,the primary genetic material found in retroviruses is $RNA$.

(B) $1$. $AIDS$ is caused by the Human Immunodeficiency Virus $(HIV)$.
$2$. The common cold is caused by rhinoviruses.
$3$. Ringworm is a fungal infection caused by genera like Microsporum,Trichophyton,and Epidermophyton.
$4$. Dysentery is typically caused by bacteria (like Shigella) or protozoa (like Entamoeba histolytica).
$5$. Typhoid is caused by the bacterium Salmonella typhi.
$6$. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
Therefore,both the common cold and $AIDS$ are viral diseases.