VIRAL DISEASES
Common viral diseases are influenza, small pox, chicken pox,
Measles, mumps, poliomyelitis, rabies, hepatitis, dengue
Influenza
Caused by Myxovirus influenzae. It is a Ribo virus
(RNA virus) with fragmented genome. Incubation period is 2-3 days.
Influenza is epidemic, endemic, and pandemic. Endemic influenza is
caused by Haemophilus influenzae, a gram Negative bacterium.
Asian flu is a viral influenza.
Influenza virus may be A, B, and C
Vaccine is available for Influenza virus A only
Smallpox
Causative agent is a DNA virus Variola virus.
Incubation period is 12 days
Edward Jenner in 1796 discovered vaccine for smallpox.
Chickenpox
Caused by a DNA virus Varicella zoaster with 14-16 days
Incubation period. Passive immunity in chickenpox is possible
through Zoaster immunoglobulin (ZIG) vaccine.
Measles
Infectious eruptive viral disease. It is caused by
RNA virus Rubella virus / Polynosa morbillorum.
Measles is transmitted to foetus through placenta.
Incubation period is 10-14 days. Antibiotics and
Sulfa drugs are effective to measles. German measles
is caused by Rubella virus. Vaccine is MMR
Mumps
Caused by RNA virus Paramyxo / Mumps virus
Infection occurs in Parotid gland (salivary gland).
Swelling of salivary gland causes difficulty in swallowing.
Secondary infection may cause sterility.
Incubation period is 12-26 days and vaccine is MMR.
Poliomyelitis
Caused by RNA virus Polio virus or Entero virus.
It causes Infantile paralysis. Poliovirus multiply in the intestine and
passes to lymph, blood and finally to CNS in dorsal horn cells of spinal
cord and brain
stem resulting in paralysis. Vaccines are
Salk vaccine – Killed, Sabin vaccine – Live.
Sabin vaccine is given as Oral Polio Vaccine.
It contains live attenuated (inactive) germs of polio.
Oral polio vaccine prevents the growth of polio virus
in the Intestinal mucosa by giving direct immunity to the intestine.
Rabies
Also called Hydrophobia because the affected
person shows fear of water. It is caused by an
RNA virus called Rabies virus. Rabies is transmitted
by infected Dog, Cat, Monkey etc. Rabies is a 100%
fatal disease. Rabies virus is called
Neurotrophic because it damage motorneurons.
Rabies vaccine was developed by Louis Pasteur.
Hepatitis
Hepatitis A is called as Endemic jaundice. It is caused by
Hepatitis A virus. It more common in children and young
adults. Incubation period is 2-6 weeks.
Hepatitis B is called Serum hepatitis. It occurs at
any stage. Incubation period is 6 weeks to 6 months.
About 80% of liver cancer is due to Hepatitis B infection.