Infections and Immunity Flashcards

Question

When are infections with HPV B19 more likely to occur?

Answer 1

Infections can occur at any time of the year but outbreaks are most common in spring

Answer 2

Transmission is via respiratory secretions from affected patients, by vertical transmission from mother to fetus and by transfusion of infected blood products

Answer 3

HPV-B19 infects the erythroblastoid red cell precursors in the bone marrow It causes a range of clinical pictures

Answer 4

Raage of presentations: o Asymptomatic infection ▪ Common ▪ 5-10% preschool children have antibodies o Erythema infectiosum: most common ▪ Viraemic phase of fever, malaise, headache and myalgia ▪ This is followed by a characteristic rash on the face ▪ This rash progresses to a maculopapular, ‘lace’-like rash on the trunk and limbs ▪ In children, complications are rare. In adults, arthralgia and arthritis are relatively common o Aplastic crisis: most common serious presentation ▪ In children with chronic haemolytic anaemias where there is increased RBC turnover e.g. SCD, thalassemia ▪ Also in immunocompromised children who are unable to produce an antibody response to neutralise the infectious agent o Fetal disease ▪ Transmission of maternal HPV-B19 infection may lead to fetal hydrops and death due to severe anaemia, but majority of infected foetuses will recover

Answer 5

• This is a clinical diagnosis via typical slapped-cheek rash with a lacy, reticular exanthem on extremities and torso seen on examination

Answer 6

Paracetamol (10-15mg/kg every 4-6hrs) or ibuprofen (5-10mg/kg every 4-6hrs) for symptomatic relief Encourage adequate fluid intake and rest Secondary arthritis may be treated with ibuprofen (4-10mg/kg every 6-8hrs) If infection persists \>3wks: o Give **IVIG** for 5d o May need a **RBC transfusion** for anaemia

Answer 7

A highly infectious disease caused by measles virus RNA paramyxovirus

Answer 8

Incubation period: 10- 14 days Infective from prodrome until 4 days after rash starts

Answer 9

There has been a rise in cases due to anxiety about the MMR vaccine

Answer 10

Older children and adults tend to have more severe disease than the very young

Answer 11

* Measles virus is transmitted via droplets and infects epithelial cells of the nose and conjunctivae. Virus multiplies in these epithelial cells and then extends to the regional lymph nodes * Note: in low income countries, where malnutrition and vitamin A deficiency leads to impaired cell-mediated immunity, measles often follows a protracted course with severe complications * Impaired cellular immune responses such as in HIV, may result in a modified/absence of rash with an increased risk of dissemination, including giant-cell pneumonia or encephalitis

Answer 12

Prodrome: irritable, conjunctivitis, fever, cough, coryzal symptoms Koplik’s spots: occur before rash, red spots often with a bluish-white central dot on erythematous buccal mucosa Rash: starts behind ears then to whole body; discrete maculopapular rash becoming blotchy and confluent; may desquamate in second week

Answer 13

o Otitis media: most common complication o Pneumonia: most common cause of death o Encephalitis ▪ RARE (1 in 5000 cases) ▪ Typically 1-2 weeks after onset of illness ▪ Headache, lethargy and irritability→seizures and coma ▪ Up to 15% mortality ▪ Serious long-term sequelae include: seizures, deafness, hemiplegia, severe learning difficulties o Subacute Sclerosing Panencephalitis (SSPE) * most of the children affected by this have had measles before the age of 2 yrs ▪ RARE but devastating ▪ Occurs 5-10 years after measles infection ▪ Caused by a variant of the measles virus that persists in the CNS ▪ Presents with loss of neurological function ▪ This progresses, over several years, to dementia and death o Febrile convulsions o Keratoconjunctivitis, corneal ulceration o Diarrhoea o Increased incidence of appendicitis o Myocarditis

Answer 14

• Examine * Measles-specific IgM and IgG serology * IgM indicates acute infection * IgG indicates an infection in the past or prior vaccination

Answer 15

* Advice * Conservative management * Safety net * Notify the local **Health Protection Team (HPT)** * Management for complications * Think about vaccination status of patient and contacts - encourage * Think about immunocompromised patients

Answer 16

Advise that measles is a self-limiting disease, but it is likely to cause unpleasant symptoms e.g. rash, fever, cough and conjunctivitis Rest and drink plenty Stay away from school for at least or at least 4 days after the development of the rash Encourage vaccinations once the acute episode has subsided Find out the immunization status of close contacts

Answer 17

**Paracetamol** (10-15mg/kg every 4-6hrs) or **ibuprofen** (5-10mg/kg every 4-6hrs) for symptomatic relief

Answer 18

Seek urgent medical advice if they develop complications such as: * Shortness of breath * Uncontrolled fever * Convulsions or altered consciousness Respiratory support can be given if pneumonia or neurological support in case of encephalitis

Answer 19

Respiratory support can be given if pneumonia or neurological support in case of encephalitis **Vitamin A** is given orally for 2d, especially in those hospitalised or \<2 years old Children should be isolated in hospital

Answer 20

In immunocompromised patients, ribavirin may be of use

Answer 21

Mumps is an acute systemic infectious disease caused by an RNA paramyxovirus

Answer 22

Occurs worldwide but incidence has declined since MMR vaccine There has been a rise since decrease in MMR vaccine uptake

Answer 23

Mumps usually occurs in winter and spring months

Answer 24

Incubation period: 15-24 days

Answer 25

Spread by respiratory droplets, direct contact or contaminated fomites It is spread by droplets to the respiratory tract where the virus replicates within epithelial cells. The virus gains access to the parotid glands before further dissemination to other tissues

Answer 26

The disease begins with a fever, malaise and parotitis; classic feature = SWOLLEN PAROTID GLANDS o This may initially be unilateral, but it will eventually become bilateral after a few days o Earache or pain when eating/drinking o Examination of the parotid duct may show redness and swelling In up to 30% of cases, the infection will be subclinical The fever usually subsides after 3-4 days Plasma amylase levels are usually elevated due to parotid inflammation When associated with abdominal pain, consider pancreatic involvement Infectivity lasts for up to 7 days after the onset of parotid swelling The illness is usually mild and self-limiting

Answer 27

o Orchitis: uncommon in pre-pubertal males but occurs in ~25% of post- pubertal males. Typically 4/5 days after start of parotitis o Hearing loss: usually unilateral and transient o Meningoencephalitis o Pancreatitis

Answer 28

* Examination * Salivary mumps IgM

Answer 29

* Advise that it is a self-limiting condition * Advise patient to rest and take in adequate fluids * Paracetamol (10-15mg/kg every 4-6hrs) or ibuprofen (5-10mg/kg every 4-6hrs) for symptomatic relief * Stay away from school for 5-7 days after the development of parotitis * Advise patient/ parents to seek help if they experience symptoms suggestive of meningitis or epididymo-orchitis * Find out the immunization status of close contacts and tell them to watch out for symptoms of mumps * Notify the local Health Protection Unit (HPU)

Answer 30

A mild, self-limiting systemic infection caused by the rubella virus (togavirus)

Answer 31

Typically occurs in winter and sprin

Answer 32

Important infection as it can cause severe disease in the fetus (see neonatal) If infection occurs in a pregnant woman, it can cause congenital rubella syndrome → triad of **hearing loss + cataracts + heart defects**

Answer 33

Spread by the respiratory route, frequently from a known contact o Transmitted by direct or droplet contact with infected body fluids, usually nasopharyngeal secretions o Patients may shed infectious virus from 7-30 days after infection o But, infants with congenital rubella syndrome may be contagious for \> 1 yr • Incubation period is 15 – 20 days o During this, virus replicates in nasopharynx and local lymph nodes and then spreads via blood stream throughout body, including in pregnant women to placenta and fetus

Answer 34

The prodrome is usually mild with a low-grade fever or none at all The maculopapular rash is often first sign of infection, appearing initially on face and then spreading centrifugally to cover whole body. Rash fades in 3-5 days Lymphadenopathy, esp of suboccipital and postauricular nodes, is prominent

Answer 35

Complications - rare in childhood (MEAT) o Arthritis o Encephalitis o Thrombocytopenia o Meningitis

Answer 36

• Serology o Should confirm diagnosis serologically if there is any risk of exposure of a nonimmune pregnant woman • FBC o May show thrombocytopaenia

Answer 37

Notify the local Health Protection Unit (HPU) Rest and take in adequate fluids Consider admitting if there is a serious complication such as haemorrhagic complications (caused by thrombocytopaenia) or encephalitis Should be kept at home until 4 days after onset of rash

Answer 38

Pregnant women with known exposure to rubella who are susceptible to rubella or who have uncertain immunity (no or unknown immunisation history and no previous serological testing), whether or not they are symptomatic, should be referred to a high-risk perinatal specialist and a paediatric infectious disease specialist to evaluate the likelihood of fetal infection and risk of sequelae. Pregnancy termination is an option for those at high risk of delivering a child with neonatal rubella.

Answer 39

* Most commonly caused by Plasmodium Falciparum * Transmitted by female Anopheles Mosquito - 40% of world's population live here

Answer 40

Causes 250,000 child deaths in Africa/yr

Answer 41

* Fever (often not cyclical) * Diarrhoea * Vomiting * Flu-like symptoms * Jaundice * Anaemia - children susceptible * Thrombocytopenia * Typical onset: 7-10 days after inoculation but symptoms can present months later (depending on Plasmodium species) Children are particularly susceptible to cerebral malaria

Answer 42

* Examination of thick blood films * The species (falciparum, vivax, ovale, malariae, or knowlesi) is confirmed by thin blood films * Repeated blood films may be necessary * Rapid diagnostic tests can also be used to establish diagnosis

Answer 43

* When travelling to endemic areas, travellers should seek latest info on malaria prevention * BNF: Prophylaxis should generally be started before travel into an endemic area; 1 week before travel for [chloroquine](https://bnf.nice.org.uk/drug/chloroquine.html) and [proguanil hydrochloride](https://bnf.nice.org.uk/drug/proguanil-hydrochloride.html); 2–3 weeks before travel for [mefloquine](https://bnf.nice.org.uk/drug/mefloquine.html); and 1–2 days before travel for [atovaquone with proguanil hydrochloride](https://bnf.nice.org.uk/drug/atovaquone-with-proguanil-hydrochloride.html) or [doxycycline](https://bnf.nice.org.uk/drug/doxycycline.html). Prophylaxis should be continued for **4 weeks after leaving the area** (except for [atovaquone with proguanil hydrochloride](https://bnf.nice.org.uk/drug/atovaquone-with-proguanil-hydrochloride.html) prophylaxis which should be stopped 1 week after leaving). For extensive journeys across different regions, the traveller must be protected in all areas of risk. * Prophylaxis reduces but does not eliminate risk of infection * Prevention of mosquito bites with repellants and bed nets is important * Insecticide treated bed nets, indoor residual spraying of houses with insecticides, destruction of mosquito larvae and breeding areas, and prompt treatment with artemisinin-based combination therapy → significant effect

Answer 44

• If uncomplicated P. falciparum disease: o Artemisinin combination therapy (such as artemether with lumefantrine or artenimol with piperaquine phosphate) o Quinine is second line(usually given with an antibiotic) • If severe P. falciparum disease: o **Parenteral artesunate** then after at least 24 hours treatment, switch to oral artemisinin combination therapy o Supportive care +/- intensive care If non-Falciparum malaria (Plasmodium vivax and less commonly by P. ovale, P. malariae, and P. knowlesi) o Artemisinin combination therapy (such as artemether with lumefantrine) or chloroquine Notify all cases to the local **Health Protection Team (HPT)**

Answer 45

**Typhoid fever is a bacterial infection caused by Salmonella type or paratyphi that can spread throughout the body, affecting many organs.**

Answer 46

Typhoid fever is highly contagious. An infected person can pass the bacteria out of their body in their poo or, less commonly, in their pee. If someone else eats food or drinks water that's been contaminated with a small amount of infected poo or pee, they can become infected with the bacteria and develop typhoid fever.

Answer 47

Worldwide, children are thought to be most at risk of developing typhoid fever. This may be because their immune system (the body's natural defence against infection and illness) is still developing. But children with typhoid fever tend to have milder symptoms than adults. Typhoid fever is uncommon in the UK, with around 300 infections confirmed each year. Most of these people became infected while visiting relatives in Bangladesh, India or Pakistan. But you're also at risk if you visit Asia, Africa or South America.

Answer 48

* Child with worsening fever * Headaches * Cough * Abdo pain * Anorexia * Malaise * Myalgia * GI symptoms: Diarrhoea or constipation - may not appear until the second week Signs: * Splenomegaly * Bradycardia * Rose-coloured spots on the trunk

Answer 49

* GI perforation * Myocarditis * Hepatitis * Nephritis

Answer 50

A diagnosis of typhoid fever can usually be confirmed by analysing samples of blood, poo, or pee. These will be examined **under a microscope for the Salmonella typhi bacteria** that cause the condition. The bacteria aren't always detected the first time, so you may need to have a series of tests.

Answer 51

Supportive care: IV fluids and antipyretics Suspected: Ceftriaxone and azithromycin Known: o Ciprofloxacin 7d treatment o If no response after 4/5d of treatment add **azithromycin** o If encephalopathic, add high-dose dexamethasone

Answer 52

Dengue is a mosquito-borne viral haemorrhagic fever (VHF) transmitted by female mosquitoes mainly of the species *Aedes aegypti* and, to a lesser extent, *Ae. albopictus.*

Answer 53

The WHO classification encompasses two clinical entities, one of which is further divided: * **Non-severe dengue** - fever followed by recovery characterises non-severe dengue. It is subdivided into: * **Dengue without warning signs** - fever with two of the following: nausea/vomiting, rash, aches and pains, positive tourniquet test, leukopenia. * **Dengue with warning signs** - the above plus any of: abdominal pain, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy, liver enlargement, increasing haematocrit with decreasing platelets. Those who deteriorate to develop severe dengue tend to have warning signs. They are likely to recover with intravenous rehydration. * **Severe dengue** - this is dengue with severe plasma leakage, severe bleeding, or organ failure. There may be shock, respiratory distress or organ damage. Further deterioration of dengue with warning signs is classified as severe dengue. A second subsequent infection with a different serotype of the dengue virus increases the risk of developing severe dengue.

Answer 54

* Patients become infected once bitten by infected mosquitoes. * The virus passes to lymph nodes and replicates, mainly in monocytes and macrophages. It then spreads to the circulation and other tissues. * Incubation period is 2-7 days. * Initial immune activation leads to a flu-like illness of varying severity (dengue and severe dengue can be very similar at the start of the illness). * There is a tendency to haemorrhage associated with severe thrombocytopenia: this can also be seen in non-severe dengue. * Proliferation of T cells and the production of cytokines may lead to vascular endothelial cell dysfunction and to plasma leakage. When severe this capillary leak characterises severe dengue. It causes an increase in haematocrit, hypoalbuminaemia, pleural effusions and ascites. * In severe cases there may be multiple organ failure. * Multiple organ dysfunction can also result from direct viral damage to organs, particularly heart, brain and liver. * Recovery from infection by one dengue serotype provides full lifelong immunity only against that serotype. Cross-immunity to the other serotypes is partial and temporary. * Subsequent infections by other serotypes increase the risk of developing severe dengue. * Infants can develop severe dengue infection during their primary infection due to transplacental transfer of maternal antibodies to a different serotype from an immune mother. These amplify the infant's immune response to the primary infection. * The pathogenesis of severe dengue is thought to be immune-mediated. Recent evidence suggests cross-reactive high pro-inflammatory cytokine producing T cells predominate in severe dengue. Studies also suggests that there may be a genetic susceptibility to severe disease^[[¹¹](https://patient.info/doctor/dengue-2#ref-11)^].

Answer 55

* FBC may show high PCV with low platelets. There may be paradoxical lymphocytosis (\>15% circulating white cells) but overall leukopenia. * Clotting studies can reveal prolongation of APTT and PT. Fibrin degradation products may be elevated. * U&E may show electrolyte disturbance. LFTs can be elevated - especially AST. * Severe cases may show reduced bicarbonate due to acidosis. * Infection may be confirmed by isolation of virus in serum and detection of IgM and IgG antibodies by ELISA, monoclonal antibody or haemagglutination. * PCR-based techniques are increasingly being used.

Answer 56

Notifiable disease **WHO group A** (no warning signs) o Tolerating adequate fluid volume, passing urine every 6hrs o Sent home o Rest and take oral fluids (rehydration products) o Monitor for warning signs o Paracetamol and tepid sponging can be used to reduce fever **WHO group B** (developing warning signs) o Hospital admission o IV/oral fluids o Monitor for progression of warning signs o Discharge once patient is afebrile for \>48hrs **WHO group C** (established warning signs) o Hospital admission to ICU o Consider blood transfusion o IV 0.9% NaCl: maintenance+ 5% fluid deficit **o100ml/kg for first 10kg 50ml/kg for second 10kg 20ml/kg for \>20kg** o Monitoring for worsening signs o Investigation for other causes o Discharge once patient is afebrile for \>48hrs

Answer 57

An acute, febrile, self-limiting, systemic vasculitis of unknown origin o Vasculitis (inflammation of blood vessel) affecting large/medium sized vessels

Answer 58

Uncommon but important to identify early, because coronary artery aneurysms are a potentially devastating complication→prompt treatment reduces incidence

Answer 59

Mainly affects children 6 months – 4 years of age, with a peak at the end of 1st yr of life More common in Japanese, and to a lesser extent Black-Caribbean ethnicity than Caucasian More common in boys

Answer 60

Incidence increasing - 3000 affected annually

Answer 61

Aetiology remains unknown Observations suggest that the disease is triggered by an unknown infectious agent Pathophysiology o Endothelial cells in blood vessels become attacked→damaged→collagen and tissue factor found in tunica media become exposed→inc chance of coagulation→this can lead to thrombosis and ischaemia of heart muscles o The artery walls also become weak→this can lead to coronary aneurysms ▪ Aneurysms occur as fibrin is deposited in the vessel walls to aid healing→fibrin causes vessels to become stiffer, less elastic and less pliable in response to blood ▪ Instead, the vessels form aneurysms ▪ Aneurysms 8mm or larger are at high risk of rupture→reducing blood flow to heart→ischaemia→MI o In other cases, vessel walls are thickened causing reduced lumen diameter → also leads to ischaemia • Self-limiting – so will resolve in 6-8 weeks but if untreated, there is a 20-25% risk of CVS complications

Answer 62

Presence of fever for at least 5 [\*](https://www.clinicalkey.com/student/content/book/3-s2.0-B9780702081804000152#fn1) days with at least four of the five following clinical features: 1. Bilateral bulbar conjunctival injection without exudate. 2. Erythema and cracking of lips, strawberry tongue and/or erythema of oral and pharyngeal mucosa 3. Cervical lymphadenopathy (≥1.5 cm diameter), usually unilateral 4. Rash: maculopapular, diffuse erythroderma, or erythema multiforme-like 5. Erythema and oedema of the hands and feet in acute phase and/or desquamation around the nails in subacute phase. \* The diagnosis can be made with 4 days of fever when at least four clinical features (particularly redness and swelling of the hands and feet) are present.

Answer 63

• Initial o FBC ▪ At beginning of disease • Anaemia Raised WCC with left-shift (i.e. inc immature WCC) Platelet count typically rises in 2nd week of illness o ESR – raised o CRP – raised o LFTs – raised liver enzymes o Echocardiogram – to assess for aneurysms • Others o Microscopic urinalysis: will show mononuclear WBCs in urine without bacteria Diagnosis is made based on clinical findings + lab tests – no specific diagnostic test Note: patients that do not completely meet the criteria→incomplete Kawasaki→ sometimes, these patients are treated anyway to prevent potential CA aneurysm

Answer 64

• First line: prompt treatment with **IV immunoglobulin (IVIG) + high-dose aspirin** o IVIG if given within **first 10 days, shown to lower risk of CA aneurysms** o **Aspirin used to reduce risk of thrombosis** – given as a high anti-inflammatory dose until fever subsides and inflammatory markers return to normal, and then continued at a low antiplatelet dose _until echo of 6w shows presence or absence of aneurysms_ ▪ Acts by inhibiting cyclo-oxygenase to prevent platelet aggregation ▪ Note: aspirin is usually contra-indicated in children as it can lead to Reye syndrome (encephalopathy + liver injury) but in this case, risk is taken and child monitored carefully * Second line treatments include corticosteroids, infliximab and plasma exchange * 3rd line treatment options include cyclospirin or anakinra or plasma exchange * Child with giant coronary artery aneurysms may require long-term warfarin and close follow-up * If fever recurs despite treatment → second dose IVIG * If persistent inflammation and fever→may require corticosteroids, infliximab (monoclonal antibody against TNFa) or cyclosporin

Answer 65

Risk assessment for myocardial ischaemia and coronary artery aneurysms is carried out: o Low risk: no further medications after 8wks of aspirin o Moderate risk: **low dose aspirin** until aneurysm regression is demonstrated, with ECG and echo follow up annually o High risk: **low dose aspirin** long term, with ECG and echo follow up twice a year Need long term **warfarin** (INR target: 2-3) May need clopidogrel

Infections and Immunity Flashcards

(92 cards)