Chickenpox is a vaccine preventable disease.
Of some common diseases occurring in the modern society Chickenpox (Varicella) is a common disease. It is infectious disease and you can acquire it from those who already have it if you haven’t got it before in your life. Let’s discuss details of Chickenpox and Chickenpox vaccine.
Table of Contents
What is chickenpox (Varicella)?
· As e all know chickenpox is a disease which is very common.
· It is also called as varicella in scientific terms.
· It is a disease characterized by fever, cough cold and peculiar rash on skin, Which can be very itchy and may get infected if hygiene is not maintained in handling it.
· In developing countries many people get infected in childhood itself.
· It is an infectious disease that means it spreads from infected person to non infected person.
About Chickenpox causative agent:
· Chickenpox is caused by Varicella Zoster virus.
· It is Human alphaherpesvirus 3 (HHV-3).
· As it’s name implies it is one of the herpes virus.
· It is spherical and 180-200 nm diameter.
· Varicella virus is double stranded DNA virus.
· It is enveloped virus, it has lipid envelop and capsule.
· Its genome encodes 70 proteins.
· Varicella Virus can stay latent or grow in human nerves.
How does Varicella zoster virus spreads?
· It spreads human to human.
· As no other host than human are known spread to or from other animals in unknown.
· It spreads by oropharyngeal secretions.
· It can spread when one comes in contact with fluid of skin lesion.
· It spread by droplets when the infected person coughs, talks or sneeze.
· It can also spread when the person directly comes in contact with oropharyngeal secretions or the fluid of the skin lesions.
What is pathogenesis of varicella zoster?
· As the diagram indicates vericella zoster virus gains entry into your respiratory tract through droplets from air.
· Vericella zoster virus comfortably sits into the mucosa of upper respiratory tract and then gains access to local lymphnodes in the mucosa there.
· After getting replicated in adequate numbers it gets disseminated in the blood stream. This is called as first stage of viremia.
· Through the blood stream it is carried to the reticulo-endothelial cells and mononuclear cells.
· Varicella zoster virus replicates extensively in these cells and is carried further to Skin.
· This is second stage of viremia.
· During this stage the skin lesions appear called as ‘Chickenpox or ‘Varicella’ and also it is carried back to respiratory and nasal mucosa so that the person becomes infectious.
· Then carried to different hosts thus completing the lifecycle of the varicella zoster virus.
· Some of these virus copies stay dormant in the neurons of the hosts and stay latent there.
· They may get activated when host’s immunity is down and not able to protect host from virus presenting as ‘shingles’ also called as ‘herpes zoster’.
What are symptoms of chickenpox?
· Symptoms of patients vary from individual to individual.
· In some it may mild in some few may be life threatening with array of complications.
· Unvaccinated individuals: In susceptible unvaccinated individuals the illness usually begins 14-16 days after the exposure to infected person. Invariably susceptible exposed individuals develop the chickenpox disease. Asymptomatic infection is rare in unvaccinated susceptible individual. The incubation period for chickenpox that is varicella zoster is 10-21 days. Initially fever moderate to high grade with masaise and abdominal pain can present. Then rash appear in form of macules on scalp, face or neck then the trunk and peripheral limbs get involved. The rash typically progresses to macules then pauples then fluid filled vesicles which look like due drop appear. It may get ruptured and umbilicated. All lesions are not in same in appearance but they are in various stages at the same time. They progress centripetally. If patient has other skin disorder or exema like conditions the rash may be sever. Usually total number of lesions are up to 300 on entire body but may be up to 1500. Lesions can appear on eyelid and conjunctiva. Chickenpox lesion affecting cornea are rare but seriously threatening vesion and may need corneal transplant.
· In vaccinated individual: Chickenpox can occur in vaccinated individuals too. If it occurs in first 14 days after vaccination it is more likely because of wild type varicella strain. This suggests the disease probably developed before vaccine could produce any immunity. From day 14 to day 42 if vaccinated individual gets chickenpox it is likely to be due to vaccine strain or wild type strain. Usually is mild and less than 30 lesions. After 42 days of getting vaccine shot if chickenpox appears it is called as breakthrough chickenpox. It primarily occurs because single dose of chickenpox vaccine provides 97% protection to very sever chickenpox but only 85% to mild disease. If given 2 chickenpox doses 8 weeks apart provides 97% to even mild disease. This is the answer why does chickenpox appear even after giving chickenpox vaccine.
· Neonatal Chickenpox: This is usually dangerous and may be life threatening condition. Especially if the mother shows chickenpox 5 days before to 2 days after delivery. Mother can transmit virus to baby through placenta 2 days before appearance of rash. During this period neonate gets infected with mother’s viremia but the mother yet not developed antibodies neonate does not get sufficient amount of chickenpox antibody for the mother. If mother gets chickenpox rash after 30 weeks of pregnancy but before 5 days to delivery probably the neonate have received antibodies to chickenpox from mother. If mother gets chickenpox manifestation before 28 weeks of gestation the antibodies produced can not be transferred to fetus through placenta. Neonates whose mothe shows manifestation of chickenpox from 5 days before to 2 days after delivery should get VZIG. These VZIG are indicated in chickenpox in neonates. Half the neonates who got VZIG will still get chickenpox rash but usually milder form. Also these should be treated with proper dosages of acyclovir drug.
What is ‘Congenital Varicella Syndrome’?
· Congenital varicella syndrome is a complication of chickenpox occurring if the susceptible unvaccinated pregnant lady gets infected during pregnancy.
· 0.4 percent fetuses of mothers who got chickenpox before 13 weeks of pregnancy and 2 perecnt fetuses of mothers who got chickenpox between 13 to 20 weeks of pregnancy show Congenital varicella syndrome.
· Characterized by Cicatricial skin rashes with scarring, Limb hypoplasia or aplasia, neurological abnormality and mental retardation autonomic abnormalities like neurogenic bladder are few of anomalies occurring in such cases. VZV antibodies persisting beyond 12-18 weeks are reliable indicator during pregnancy to predict fetal anomalies.
What are complications of Chickenpox?
· Explaining the complication is the main purpose of this article as we want to make you aware why not to ignore chickenpox.
· As we know the disease occurs as chickenpox or its reactivation complications are known to occur in both stages.
· Complications are particularly more common and more severe in individuals with immune-compromised status.
· Varicella hepatitis is common but usually milder condition subsiding in healthy individuals.
· Mild thrombocytopenia can be found in investigation in 1-2 percent individuals.
· Purpura, haemorrhagic vesicle, hematuria and gastrointestinal bleed are rare but known complication.
· Other complications of chickenpox are cerebellar ataxia, encephalitis, pneumonia, nephritis, nephrotic syndrome, hemolytic-uremic syndrome, arthritis, myocarditis, pericarditis, pancreatitis, orchitis, and acute retinal necrosis.
· Secondary bacterial infection: Streptococci are known to cause infection at local site on the lesion and later leading to invasive disease. It may worsen to cellulitis and gangrene in some cases. Varicella gangrenosa, pneumonia, arthritis, bacterial sepsis, osteomylitis, sepsis, septaesemia, necrotizing fasciitis.
· Encephalitis and cerebellar ataxia: These are two known complications of chickenpox. Seizures, nuchal rigidity, slurred speech, altered consciousness are the few manifestations. These generally occur after 3-4 days of occurrence of rash but may after rash is healed. Usually recovery is rapid and occurs in 2-3 days. Rarely reyes syndrome can occur.
· Pneumonia: One of the most severe complications of chickenpox known as varicella pneumonia usually occurs in adults but may occur in children too. Present like other pneumonias cough, dyspnoea, chest pain, pluritis. Smoking is usually known risk factor for this complication to occur.
What is progressive varicella?
· It is complication of chickenpox which can be potentially fatal.
· It occurs in adolescents and adults and immunocompromised children, pregnant women and also neonates, children with malignancy and and those who are on chemotherapy.
· There is visceral organ involvement along with haemorrhagic vesicular rash, coagulopathy.
· Sever abdominal pain due to involvement of mesenteric lymphnodes and liver are common manifestation.
· It usually occurs in with children with reduced cellular immunity or children who have received corticosteroids during the incubation period.
What is Herpes Zoster?
· This is reactivation of latent chickenpox many times years after initial infection.
· It is usually limited to single or two dermatomes of the body.
· Half of adults who get herpes zoster usually develop complication post herpetic neuralgia.
· It usually starts as sever local itching and pain followed by visible macules and leading to very painful and itchy vesicles.
· Many adults experience one or two or more episodes of this zoster.
· Children who have got chickenpox in neonatal period or first year of life are more likely to get Herpes zoster.
· But in children post herpetic neuralgia is rare.
· Some subjects may get retinitis, hepatitis, encephalitis, visceral dissemination and coagulopathy. But these manifestations are rare and mostly occurring in children with immune-compromised status, those on chemotherapy or those with HIV AIDS.
How is chickenpox diagnosed?
· Diagnosis of varicella is usually clinical and no tests are required to diagnose varicella.
· Tests can be needed when clinical picture is confusing and diagnosis is needed to decide further course of action.
· Initial stages may show leucopenia followed by relative or absolute lymphocytosis.
· Mild elevation liver enzymes can be noted.
· Additionally tests are needed to diagnose and monitor the complications like encephalitis, hepatitis, coagulopathy or visceral organ involvement.
What is treatment of chickenpox?
· Acyclovir is the treatment drug for the chickenpox but every patient does not need acyclovir.
· Only individuals with moderate to sever vericella need to be treated with acyclovir.
· Additionally those who are likely to develop complications and those who are less than 12 month old or more than 12 year old, those who are immune-compromised, pregnant need treatment with acyclovir.
· Additionally those who have got sever complications of chickenpox also need treatment with acyclovir.
· Treatment of Herpes zoster with acyclovir reduces the chances of getting post herpetic neuralgia.
How to prevent chickenpox?
· Rather than varicella infection it is needed to prevent chickenpox complications.
· The prevention strategies for chickenpox depends on different factors and also depend on whether person is already exposed.
· There is two types of vaccination to prevent varicella.
· Passive immunity that is to confer immediate immunity by giving antibody from outside is immunoglobulin VZIG.
· Active immunity that is giving chickenpox vaccine to susceptible individual and making him to get immunity against chickenpox is chickenpox varicella vaccine.
What is VZIG varicella zoster immunoglobulin?
· Varicella zoster immunoglobulin AKA VZIG are readymade antibodies against chickenpox virus varicella.
· Those who have got exposed to varicella patients who are susceptible and likely to get chickenpox need to take VZIG.
· This VZIG provide immediate immunity to chickenpox, it is passive method to give immunity to susceptible individual.
· Neonates who have got varicella exposure and got VZIG still half of them may develop varicella but the sever lefe threatening complications of varicella which are very common in neonates are prevented by VZIG.
About chickenpox varicella vaccine
· Varicella vaccine is live attenuated vaccine.
· A similar but live virus with no or reduced capacity to cause actual disease is injected sc or im.
· This live virus infects the person who received vaccine then and multiplies inside the body.
· The host who received vaccine then produces immunity against this vaccine virus in 2-4 weeks.
· As this virus is similar to the actual chickenpox virus now the immune system is ready to fight to actual infection in future as it also develops memory regarding how to fight this type of virus that is chickenpox.
· Chickenpox vaccine is given in injection form in 2 doses at least 8 weeks apart.
· It is generally given at 15 months of age and second dose at 4.5 years of age.
· One dose protects nearly 97 percent of hosts from sever complications of chickenpox and 85 percent of mild infections.
· So even after getting single dose of chickenpox vaccine getting mild disease is common in nearly 15 percent patients.
· After second dose nearly 95 percent those received vaccine are protected from mild and 97 percent are protected from sever disease.
What are side effects of chickenpox varicella vaccine?
· Usually serious complications are rare in case of varicella.
· Common complications are local injection site pain and sometimes swelling lasting for up to 3 days.
· Fever may be noted in some children which can be easily managed on fever medicine given at home.
· Chickenpox like rash which are usually less than 20 papules can appear between 8-21 days of vaccine date.
· Rests other serious complication like anaphylaxis are rare.
· Complications of chickenpox disease are far more common than complication of chickenpox vaccine.
Why chickenpox even after vaccine?
Dr Yatin Bhole
We are very near to Akurdi, Kiwale, Punawale.