What is the mode of transmission of mumps, its incubation period, and the recommended isolation and vaccination precautions?

Mumps Transmission and Infection Control

Mode of Transmission

Mumps is transmitted via respiratory droplets and direct contact with saliva, requiring immediate implementation of droplet precautions and standard precautions for all suspected or confirmed cases. 1, 2

• The virus spreads through exposure to respiratory droplets when infected persons cough, sneeze, or talk, and through direct contact with contaminated saliva. 3
• Humans are the only known hosts for mumps virus. 3
• Transmission occurs from 2 days before through 5 days after parotitis onset, though the virus can be isolated from 7 days before through 8 days after symptom onset. 2, 4
• The highest viral loads and greatest transmission risk occur closest to parotitis onset and decrease rapidly thereafter. 4
• Transmission can occur during the prodromal phase and with subclinical infections, making infection control challenging since 15-20% of infections are asymptomatic and only 30-40% present with typical parotitis. 4, 5

Incubation Period

• The incubation period is most commonly 16-18 days, with a range that supports surveillance extending to two incubation periods (5-6 weeks total) during outbreak control. 6, 7

Isolation Precautions

Isolate patients with mumps using standard precautions plus droplet precautions for 5 days after onset of parotitis. 5, 1, 4, 6

Specific Isolation Requirements:

• Apply gown and gloves for all patient contact in addition to droplet precautions. 1
• Negative-pressure rooms are NOT required for mumps patients, unlike airborne diseases such as measles. 1
• This updated 5-day isolation period (changed from the previous 9-day recommendation in 2007-2008) is based on evidence showing that most transmission occurs before and within 5 days of parotitis onset, with viral loads decreasing rapidly thereafter. 4, 6
• The 5-day isolation period demonstrates better compliance (86%) compared to the previous 9-day recommendation (65%), particularly in university settings. 6

Healthcare Worker Management

Only healthcare workers with documented immunity may care for mumps patients, defined as two documented doses of MMR vaccine administered ≥28 days apart, laboratory evidence of immunity, laboratory-confirmed prior disease, or birth before 1957. 1

Post-Exposure Protocol for Healthcare Workers:

• No documented immunity (0 doses):

  • Offer first MMR dose immediately (though post-exposure vaccination does NOT provide effective prophylaxis due to delayed antibody response). 1
  • Exclude from duty from day 12 through day 26 after the most recent exposure. 7, 1

• One documented dose:

  • Worker may remain at work. 1
  • Administer second MMR dose immediately. 1

• Two documented doses:

  • No further action required; documented vaccination supersedes serology even if titers are negative or equivocal. 1

• Healthcare workers who develop parotitis must be excluded from work for 5 days from symptom onset. 1

• Do NOT perform serologic screening before vaccination during outbreaks; rapid vaccination is essential. 1

• Immune globulin is NOT effective for post-exposure mumps prophylaxis. 1

Vaccination Precautions

Two doses of MMR vaccine are recommended for all healthcare personnel without documented immunity, with 2-dose vaccine effectiveness ranging from 79-95%. 7, 1

Key Vaccination Points:

• One-dose vaccine effectiveness is 80-85% against mumps. 7
• Recipients of MMR vaccine do NOT shed vaccine virus and require no work restrictions after vaccination. 1
• Do NOT administer MMR vaccine to pregnant women due to theoretical risk of fetal harm from live-virus vaccine. 5
• Pregnant healthcare workers without documented immunity should be excluded from caring for mumps patients. 1
• Mumps infection during the first trimester increases risk of fetal death but is NOT associated with congenital malformations. 1

Outbreak Control Measures

During outbreaks, exclude susceptible persons who are exempt from vaccination from the affected institution until at least 26 days after onset of parotitis in the last case. 7

• Excluded students can be readmitted immediately after vaccination. 7
• Active surveillance should continue until two incubation periods (5-6 weeks) have elapsed since onset of the last case. 7
• Recent outbreaks have occurred in highly vaccinated populations (particularly college students and young adults in close-quarter settings) due to waning immunity and primary vaccine failure, underscoring the need for rapid outbreak response. 7, 1, 2

Critical Pitfalls to Avoid

• Do NOT assume parotitis is always present—only 30-40% of mumps infections produce typical parotitis, while 15-20% are asymptomatic and up to 50% present with nonspecific respiratory symptoms. 5
• Do NOT assume immunity based on vaccination alone—outbreaks have occurred in populations with 2-dose vaccination coverage exceeding 90%. 7, 2
• Do NOT overlook the need for immediate reporting—probable or confirmed cases must be reported immediately to state and local health departments. 5, 3
• Laboratory confirmation is preferred over clinical diagnosis alone, using viral isolation, significant rise in serum mumps IgG antibody, or positive mumps IgM antibody. 7, 5