Outbreaks, Alerts and Hot Topics

Salmonella Outbreak Related to Wild Songbirds in the U.S. and MMR Outbreak in the Democratic Republic of Congo

Angela Myers, MD, MPH | Director, Division of Infectious Diseases | Professor of Pediatrics, UMKC School of Medicine | Medical Editor, The Link Newsletter

On April 1, the Centers for Disease Control and Prevention sent out a notice that there is an ongoing Salmonella Typhimurium outbreak investigation related to wild songbirds (e.g., pine siskins, also known as the North American goldfinch), a North American migratory bird in the finch family with a rather random winter range.¹

The outbreak started in late December and involves eight states so far (California, Kentucky, Mississippi, New Hampshire, Oklahoma, Oregon, Tennessee, Washington). Nineteen infections have been identified with ages ranging from 2 months to 89 years (median age 16 years). Two-thirds of the infections have occurred in women, and eight people required hospitalization. No deaths have occurred. Typical symptoms of salmonellosis include fever, abdominal cramping, and diarrhea that may have blood in it. The typical incubation period is a few hours to one week, and most people recover within one week. Why the concern? The reported cases are likely the tip of the iceberg given the geographically wide distribution and the likelihood that those with mild illness may not seek out medical care. So, it is possible for cases to appear in Kansas and Missouri.

Salmonella Typhimurium and other Salmonella sp. are transmitted between birds, from birds to pets, and to people. This outbreak has caused illness in birds and people. Direct contact with wild songbirds and bird feeders has been identified as the cause of illness based on whole genome sequencing of isolates from birds and humans. Although bird baths have not been implicated at this point, bird baths can be a source of Salmonella infection, and birds do not need to be sick to transmit infection. As we shift our focus to being outside this spring and summer, there are some things you can do to keep you and your pets safe and still enjoy hearing these birds.

• Clean your bird feeder and bird bath weekly with warm soapy water followed by soaking it in a solution of one part bleach to nine parts water in a sink or tub apart from the kitchen. Let your bird feeder/bath dry out in the sun to kill any remaining bacteria. (Note: make sure to disinfect the sink or tub afterward).
• Remove old seed from the bird feeder prior to cleaning and remove fallen seeds/hulls from the ground around the feeder.
• Wash your hands immediately after handling your bird feeder or bird bath.
• Keep pets away from the bird feeder and bird bath.
• Remove your bird feeder and bath for two weeks if you find a sick or dead bird in your yard and call your state wildlife agency using this link to receive further instructions. https://www.fishwildlife.org/landing/membership/member-list
• Wear gloves or cover your hand with a bag before handling a sick or dead bird.

Pine siskin. Wikipedia source.

MMR Outbreak

A new measles outbreak has surfaced in the Democratic Republic of Congo less than one year following the most recent outbreak.² Massive vaccine campaigns through Médecins Sans Frontières (Doctors without borders) have provided immunizations for millions of children in remote areas in recent years, reducing the number of infections overall. However, measles is the most contagious virus (R0 12-18, i.e., one can expect 12-18 secondary cases for each index case that is introduced into an unimmunized population) and in order to stop spread of disease, complete two-dose immunization of 95% of children is needed to achieve the classic “herd immunity.” More than 13,000 infections have occurred since the beginning of 2021, and in the last two years nearly half a million children were diagnosed with measles, leading to nearly 8,000 deaths in this one country. The vast majority (75%) of deaths were in young children <5 years of age. 

While this outbreak is in a remote part of the world, it can have ramifications for the U.S. Consider that routine vaccinations plummeted in the U.S. at the beginning of the COVID-19 pandemic, dropping to less than half of what they were pre-pandemic in children >2 years of age, and slightly less than half in children <2 years.³ A paper published in Vaccine in February evaluated the potential impact of the COVID-19 pandemic on coverage of measles-containing vaccines.

Prior to the pandemic, the immunization rate for measles in the U.S. was >90%. This modeling study assumed a 50% decline in the baseline measles immunization rate, a stable birth rate using 2018 birth numbers, and accounted for potential intermittent stay-at-home orders throughout 2020. The authors show that as immunizations fall due to reduced well-child visits from stay-at-home orders, the overall proportion of children vaccinated against measles could fall below 80%. This would then require a sustained catch-up effort of a 15% increase in well-child visits above normal baseline to raise the rate of children protected against measles to previous herd immunity (95%) levels.

Pediatricians are the experts in providing vaccines to children. Focusing on children who are nearing school age for the second MMR dose, in addition to first doses in those <2 years, will help to ensure maintenance of herd immunity across the U.S. As states and countries start to dip their toe in the water of re-opening, we are reminded that it only takes one plane ride to start a new outbreak in another country or area of the world.

References:

1. Accessed April 10, 2021. https://www.cdc.gov/salmonella/typhimurium-04-21/index.html.
2. Accessed April 10, 2021. https://www.reuters.com/article/us-congo-measles/measles-resurgent-in-congo-eight-months-after-epidemic-declared-over-idUSKBN2BP153.
3. Santjoli JM, Lindley MC, DeSilva MB, et al. Effects of the COVID-19 pandemic on routine pediatric vaccine ordering and administration-United States, 2020. MMWR Morb Mortal Wkly Rep. 2020;69:591-593.
4. Carias C, Pawaskar M, Nyaku M, et al. Potential impact of COVID-19 pandemic on vaccination coverage in children: A case study of measles-containing vaccine administration in the United States (US). Vaccine. 2021;39:1201-1204.