Stanislaus County health officials have shed more light on a surge in Shigella infections this year.
In an update, officials said 50 people have been hospitalized for the gastrointestinal illness in the past 12 months. The residents were predominately infected with the Shigella sonnei species that was associated with outbreaks in other California counties in 2014 and 2015.
Four species of Shigella bacteria, including sonnei, cause the highly infectious illness characterized by mild to severe diarrhea, fever and abdominal pain.
Dr. John Walker, county public health officer, said the emerging Shigella sonnei infections are a concern because the strain was previously known for fairly mild illness, but it gained an ability to produce the Shiga toxin that causes complications in patients.
Every year sees about 500,000 Shigella infections, resulting in 6,000 hospitalizations and 70 deaths in the United States.
“What is different is that we usually don’t see this particular species (Shigella sonnei) causing hospitalization,” Walker said, explaining why state health experts are watching the local outbreak.
The California Department of Public Health is assisting with the investigation of the 128 cases in Stanislaus County, where the illness seems to spread from person to person. “Other counties are affected and (the state) is trying to understand the cause and how it’s spread,” Walker said.
A spokesman for Memorial Medical Center said the Modesto hospital has seen 13 cases in its emergency department since November. Nine patients were admitted to the hospital.
Stanislaus County, which typically has 10 to 15 cases of Shigella each year, recorded 47 cases by mid-August of this year, prompting the Health Services Agency to warn the public. The outbreak affecting everyone from children to seniors peaked at 22 reported cases in September and decreased to 12 in October and 10 in November. The county health agency recently issued a second alert urging residents to take precautions, such as thorough hand-washing, so the disease is not spread at holiday gatherings.
Patients normally suffer with the illness for five to seven days, but it can cause serious complications such as dehydration, anemia, kidney failure and fever-related seizures in children. The disease is spread person to person when infected individuals don’t wash their hands after using the restroom and touch objects or contaminate food that is then eaten by other people.
Some Shigella outbreaks are linked to contaminated food at restaurants, tainted drinking water, or nursing home or child care facilities, but there are no patterns suggesting that has happened in Stanislaus County, Walker said.
Jeanette Camarillo of Modesto said her 7-year-old son, who caught the illness last month, had diarrhea for more than two weeks and would cry all night with stomach cramps. Her 2-year-old son came down with bloody stools, or mostly blood in his diapers, Camarillo said. Her youngest son was taken to Memorial Medical Center and was immediately sent to Valley Children’s Hospital near Madera, where he was treated for three days.
The 2-year-old was treated with antibiotics after tests detected the Shiga toxin. Camarillo, who has five children, said she did everything to keep the illness from spreading to other family members in the Pelton Avenue dwelling in west Modesto, such as wearing gloves when changing diapers and frequent use of hand sanitizer.
Walker said outbreaks of Shigella sonnei infection began in 2014 in San Diego County, yielding a two-year total of 426 cases. San Joaquin County was hit with the same bacterial strain in 2015, resulting in 185 residents with Shigellosis, up from 30 the previous year.
State officials alerted Stanislaus County, which confirmed its first Shigella sonnei infection in June 2015, Walker said.
A genomic study by researchers at UC Davis and the state health department concluded the same cluster of Shigella sonnei struck in San Diego and the San Joaquin Valley, while a different cluster was tied to outbreaks in the Bay Area.
In a news release Wednesday, Vishnu Chaturvedi, director of the state’s microbial diseases lab, said Shigella sonnei bacteria normally cause more mild disease but started to produce the Shiga toxin. The species acquired a gene to produce toxin most likely through genetic exchanges with E. coli and other Shigella species, Chaturvedi said.
According to the recent study, the Shigella strain associated with outbreaks in San Francisco contained genes that made it resistant to certain antibiotics. Those resistant genes are similar to what’s found in Shigella strains in Southeast Asia.
Dr. Navneet Gill, an infectious disease specialist at Doctors Medical Center of Modesto, said some patients need hospital care for dehydration, and the toxin can destroy red blood cells leading to hemolytic uremic syndrome affecting the kidneys.
“It usually affects children more than adults,” Gill said.
By getting residents to thoroughly wash their hands with soap and running water, the county hopes the caseload will return to normal.
Krista Dommer, a spokeswoman for San Joaquin County’s public health agency, said that county has confirmed 65 Shigella cases in 2016, a third of last year’s total. Staff members in that county never found a source for the infections, Dommer said.
“We hope it won’t be a problem in 2017,” Walker said.
Ken Carlson: 209-578-2321, @KenCarlson16
Symptoms: Diarrhea, fever, abdominal pain within two days of exposure
Potential complications: Dehydration, seizures in children with high fever, anemia, kidney failure
Incidence: 4.82 cases per 100,000 population in United States (2013)
Treatment: Supportive care. Due to resistance to common antibiotics, alternative drugs such as ciprofloxacin and azithromycin are used.
Prevention: Thorough hand-washing with soap and running water after using the restroom, changing diapers or before eating. Sing “Happy Birthday” twice to time hand-washing.
Sources: Centers for Disease Control and Prevention; Stanislaus County Health Services Agency