Paramyxovirus

Etiology

The family Paramyxoviridae contains two subfamilies that are relevant to humans: Pneumovirinae and Paramyxovirinae. The subfamily Pneumovirinae gives rise to the genus Pneumovirus (respiratory syncytial virus).  The subfamily Paramyxovirinae gives rise to the genus Morbillivirus (measles virus/ rubeola), to the genus Respirovirus (para-influenza viruses 1 and 3), and to the genus Rubulavirus (mumps virus and para-influenza viruses 2 and 4).[3]  The transmission occurs via respiratory droplets or direct contact. [3]

Epidemiology

Measles: Worldwide, it is estimated that Measles accounted for 2.6 million deaths prior to immunizations. There are limited cases in the United States due to the vaccination program, however, there have been peaks of cases in recent years with immunization hesitancy among certain populations of parents. It is a reportable disease in the United States along with most countries across the globe. [4]

Measles is transmitted via respiratory droplets or close contact from person to person. High-risk groups are malnourished, especially low in vitamin A supplement, or unvaccinated children, pregnant women, and immunocompromised individuals. An infected person is infectious four days prior and after developing a rash, during which, the classic cough, coryza, and conjunctivitis are also present. 

Mumps: Since the introduction of its vaccine in 1967, mumps has decreased by 99.8% in documented infectious cases in the US. It is also a reportable disease in the United States.

Mumps is transmitted via respiratory droplets or direct contact with saliva or fomites. Some infected individuals, up to 1/3, could be asymptomatic while contagious. The most contagious days are typically a couple of days before the onset of symptoms, while the virus is primarily in the upper airways. Once the virus enters into the regional lymph nodes, it spreads throughout the body causing inflammation in the central nervous system, salivary glands, parotid glands, pancreas, testes/ovaries, and mammary glands. [5]                                                    

Parainfluenza virus/Croup: Parainfluenza virus accounts for at least 1/3 of acute respiratory infections in the pediatric population each year. Parainfluenza types 1, 2, and 3 account for approximately 75% of the yearly croup cases as well as laryngotracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis. The remainder of croup cases (approximately 25%) have a bacterial etiology. In the United States, 7% of pediatric populations under age 5 will be admitted for croup. Type 3 parainfluenza virus could also cause bronchiolitis and pneumonia. Type 4 typically results in mild upper respiratory infection in adults and children.[6]

Parainfluenza virus is transmitted via respiratory droplets or direct contact. [7]

Respiratory Syncytial Virus: Respiratory Syncytial Virus accounts for 33 million infections across the world as well as nearly 200,000 pediatric death. 90% of the pediatric population under 2 years of age that contract RSV will present with an upper respiratory illness, mainly.  Occasionally,  lower respiratory symptoms will also be present. On most occasions, it presents as bronchiolitis.

Reinfection occurs frequently due to lack of long term immunity in humans, as the virus reinfects older children and adults frequently. RSV is transmitted via respiratory droplets. Patients with a history of prematurity, immunosuppression, and the elderly are at higher risk of morbidity and mortality from RSV infections. [8]

History and Physical

Measles: Typically, measles presents with the classic three “C”s: cough, coryza (inflammation of the mucous membranes lining the nasal cavity) and conjunctivitis. Fevers are common, along with a generalized maculopapular rash. The three “C”s usually appear the first 10 – 12 days after infection, followed by the rash. On physical exam, the Koplik spots, tiny grains of white papules surrounded by red halo on the buccal mucosa, can be noted a day or two prior to the maculopapular rash on the skin. The rash spreads on the face first, then caudally. The disease usually resolves on its own within a week after the onset of rash.[4]

Mumps: Mumps has a nonspecific prodrome that occurs a few days prior to parotitis. Prodrome symptoms may include fever, headache, myalgias, weakness, malaise, and anorexia. Parotitis is present in 70% of Mumps infection, as it is the most common manifestation. Inflammation of the parotid glands causes cheek swelling, usually bilateral, along with inflammation of the mucosa of Stenson’s ducts.  The submaxillary and submandibular glands may be involved as well. One of the common complications of parotitis is recurrent sialadenitis.[5]

Parainfluenza/Croup: Croup typically presents with a "seal-like barking" cough, hoarseness of the voice, stridor, and difficulty breathing.  This results from subglottic edema which narrows the upper airway. Other nonspecific syndromes may include fever, an increased respiration rate, and and increased heart rate [6][7]

RSV: RSV typically causes upper respiratory symptoms, which may including, fever, chills, myalgia, rhinorrhea, congestion, and cough. Occasionally, conditions could progress to lower respiratory infections that leads to bronchiolitis and in severe cases, viral pneumonia with dyspnea, usage of accessory muscles, and wheezes.[8]

Evaluation

Measles

CBC: leukopenia, lymphopenia, thrombocytopenia

CMP: electrolyte abnormalities from poor PO intake, diarrhea

IgM antibodies in serum or plasma, within 3 days after rash onset up to 3 weeks

Gold standard: plaque reduction neutralization assay – highest sensitivity

PCR of viral RNA from throat, nasal, nasopharyngeal, or urine sample [4]

Mumps

The diagnosis is clinical

Obtain Buccal/oral swab for RT-PCR and IgM antibody, IgG antibody, and serum viral RT-PCR

Confirmation technique: Reverse transcriptase-polymerase chain reaction (RT-PCR) of serum and oral secretions and serum IgM antibodies [5]

Parainfluenza Virus (Croup)

The diagnosis is typically clinical [7]

The chest x-ray may show a narrowing of the trachea, also known as the "steeple sign"[6]

Respiratory Syncytial Virus

The diagnosis is clinical

Nasal rapid antigen testing and PCR testing can be used should management change

The chest x-ray may show hyperinflation of the lungs and patchy atelectasis[8]

Treatment / Management

Prevention with MMR vaccine. Contraindicated in pregnant patients, immunocompromised patients as it is a live attenuated virus vaccine. 

Measles: supportive care along with Vitamin A supplements to avoid SSPE for malnourished patients. [4] 

Mumps: supportive care with cold compressions and analgesic medications. [5]

Parainfluenza virus/croup: Racemic epinephrine, dexamethasone, oxygen, humidified air, and supportive care. [7] [6] 

RSV: Supportive care, Ribavirin (antiviral), Palivizumab (immune prophylaxis) [8][9]

Differential Diagnosis

Measles: influenza, rubella, SSPE, scarlet fever, drug rashes, serum sickness, roseola infantum, infectious mononucleosis, erythema infectiosum, echovirus, coxsackievirus, Kawasaki, rocky mountain spotted fever, toxic shock syndrome, meningococcemia, encephalitis [4]

Mumps: bacterial parotitis, HIV parotitis, Mikulicz syndrome, salivary gland tumors, drug-related parotid enlargement, meningitis, encephalitis, pancreatitis, orchitis, oophoritis, prostatitis, nephritis, thyroiditis, hypothyroidism, meningoencephalitis [5] 

Parainfluenza virus: influenza, pneumonia, bronchitis [7]

Croup: airway foreign body, epiglottitis, retropharyngeal abscess, bacterial tracheitis, bronchiolitis, influenza, Respiratory Syncytial Virus, subglottic stenosis, angioedema [6]

RSV: bronchiolitis, pneumonia, influenza, asthma, croup, bronchitis [8]

Prognosis

Measles: usually excellent prognosis [4]

Mumps: usually excellent prognosis [5]

Parainfluenza virus/Croup: usually excellent prognosis [6]

Respiratory Syncytial virus: usually excellent prognosis [8]

Complications

Measles: complications occur commonly in immunocompromised and young infants, pregnant women, and malnourished children. Complications include but are not limited to pneumonia, blindness, encephalitis, severe diarrhea, dehydration, severe respiratory infection, maternal death, spontaneous abortion, intrauterine fetal death, low birth-weight infants, keratoconjunctivitis, measles inclusion body encephalitis, acute disseminated encephalomyelitis, subacute sclerosing panencephalitis [4]

Mumps: meningitis, encephalitis, deafness, pancreatitis, abscess, infertility, spontaneous abortion, thyroiditis [5]

Parainfluenza virus/Croup: pneumonia, pulmonary edema, bacterial tracheitis, death [7] [6]

Respiratory Syncytial virus: upper and lower respiratory tract infection, bronchiolitis, viral pneumonia, acute respiratory failure [8][4][5][6]