CDC HAN: Domestically Acquired Cyclosporiasis Cases in Multiple U.S. States, 2026

#19,249

Yesterday the CDC released a HAN Advisory on a multi-state outbreak of cyclosporiasis that we've been following for the past two weeks (see here and here). 

Due to its length, I've only posted the summary and the advice to the public. Clinicians, public health workers, and other interested parties should follow the link to read it in its entirety.

For now the source of the infection remains unknown, but is likely linked to lettuce, berries, or other produce.

Domestically Acquired Cyclosporiasis Cases in Multiple U.S. States, 2026
July 14, 2026

At a glance
Distributed via the CDC Health Alert Network
July 14, 2026
CDCHAN-00531

Summary

The Centers for Disease Control and Prevention (CDC) is notifying clinicians, public health practitioners, and laboratorians of cases of domestically acquired cyclosporiasis in multiple U.S. states. Since May 1, 2026, CDC has received reports of 1,645 confirmed domestic cases of cyclosporiasis and is aware of more than 5,100 cases that require further analysis to confirm the illness as domestically acquired cyclosporiasis. This is substantially higher than the 249 cases reported nationally by this same time last year. 

Of the 1,645 case-patients with available information, 141 (9%) were hospitalized, and none have died. CDC, the U.S. Food and Drug Administration (FDA), and state and local health departments are working together to investigate multistate outbreaks of Cyclospora infections and to identify the sources of illness. Because cyclosporiasis is often underdiagnosed and underreported, the true number of illnesses is likely higher than what has been reported to CDC. This Health Advisory provides background information about cyclosporiasis, current U.S. surveillance data, and recommendations for clinicians, laboratorians, and public health departments to support recognition, diagnosis, and reporting.

Background

Cyclosporiasis is a gastrointestinal illness caused by the microscopic parasite Cyclospora. People can become infected by consuming food or water contaminated with the parasite. This illness is not usually spread directly from person to person. Case counts typically rise during spring and summer months, and CDC considers May 1-August 31 the annual cyclosporiasis season. Previous outbreaks have been linked to consuming contaminated fresh produce.

Symptoms of cyclosporiasis typically begin about 1 week after exposure. Onset of symptoms can occur 2-14 days after being exposed. The most common symptoms include watery diarrhea, which can be frequent, along with loss of appetite, weight loss, bloating, nausea, and fatigue. Less common symptoms include low-grade fever and vomiting. Without treatment, symptoms can follow a remitting-relapsing course that can last from a few days to a month or longer. Illness can be severe, but is not usually life-threatening. Complications can include malabsorption, cholecystitis, and reactive arthritis. Laboratory detection of Cyclospora in stool can be challenging even in symptomatic patients, and standard ova and parasite exams might not detect it reliably. Clinicians should specifically request diagnostic testing for Cyclospora when it is clinically suspected.

Since May 1, 1,645 lab-confirmed cases were reported to CDC in people who acquired cyclosporiasis in the United States. Cases were reported by 34 states. Case-patients developed illness after eating food in the United States and did not report any travel during the previous 14 days. Case-patients ranged in age from 2-95 years, with a median age of 44 years, and 56% were female. Of 1,645 case-patients with information available, 141 (9%) were hospitalized. No deaths have been reported. This is substantially higher than the 249 cases reported nationally from May 1–July 16, 2025.

CDC is working closely with FDA and state health authorities to investigate multiple clusters of cyclosporiasis. CDC has posted an investigation notice about an outbreak with more than 400 cases in at least four U.S. states that appear to be epidemiologically linked, suggesting that there could be a common source of these infections.

        (SNIP)

Recommendations for the Public

• Visit a clinician if you have prolonged or watery diarrhea, especially if it lasts more than a few days.

• Reduce your risk by thoroughly washing fresh produce under clean running water before eating and by following safe food handling practices. Be aware that chemically disinfecting or sanitizing produce might not fully eliminate Cyclospora. It is important to thoroughly wash produce even if it is labeled as pre-washed.

       (Continue . . . )

 

New Zealand Reports 1st Detection of H5N1 in a `Sea Bird'

 

#19,248

We've a bare-bones report today from New Zealand's Ministry for Primary Industries on that country's first detection of H5N1, which come less than a month after Australia's first report. 

While the bird species isn't specified (`ocean going sea bird'), and no collection dates are provided, this suggests the eastward spread of H5N1 across more than 3,300 miles of oceania in a matter of a few weeks. 

The official statement follows:

SITUATION UPDATE: 15 July 2026

A single ocean-going sea bird has tested positive for H5 bird flu in New Zealand.

The bird was found on Petone Beach in Wellington and reported to our exotic pest and disease hotline. Subsequent testing confirmed H5 bird flu (H5N1 avian influenza clade 2.3.4.4b).

This is the first detection of H5 bird flu in New Zealand. It hasn't been found in any other birds and there are no detections in poultry.

The risk to human health remains low.

New Zealand is well prepared to respond and will react quickly to protect poultry production, and to reduce impacts on wildlife and communities.

While this was fully expected after the arrival of the virus to mainland Australia (see New Zealand: DOC to vaccinate ‘at risk’ birds against bird flu), it is disappointing how quickly the last H5-free dominos on earth are falling. 

H5N1 marches on. 

 

Australia: 8th Confirmed Bird Flu Detection in WA - Nationally Confirmed (N=14)

 

#19,247

Overnight Western Australia has confirmed an 8th H5N1 detection in a bird (petrel), found at Lancelin Beach (70 km North of Perth), and are awaiting confirmation from CSIRO on an additional a dead giant petrel, found on WA South Coast.

This brings the nation's total to 14 confirmed. 

This from the WA government website, after which I'll have more on some of the challenges of collecting, transporting, and testing wildlife samples in Australia.

New bird flu cases at Lancelin and Denmark
Media release

 
Western Australia has recorded a new positive detection of H5 bird flu in a migratory seabird at Lancelin bringing the State’s total to eight confirmed cases.

Last updated: 15 July 2026

Western Australia has recorded a new positive detection of H5 bird flu in a migratory seabird at Lancelin bringing the State's total to eight confirmed cases.

Testing at the CSIRO's Australian Centre for Disease Preparedness this week confirmed the 'presumed positive' detection in a dead giant petrel, found at Lancelin Beach, north of Perth.

While testing was unable to fully determine the specific H5 bird flu strain, likely due to the sample quality from a decomposed carcass, it will be treated as a positive case.

On the WA South Coast, a dead giant petrel found at Parry Beach in Denmark has also tested positive for the H5 strain.

In this case, additional testing by CSIRO to confirm the H5 bird flu strain has not been finalised and may also not be possible due to carcass degradation. It is likely to be treated as a presumed positive detection.

Both cases were reported by members of the public to the Emergency Animal Disease (EAD) Hotline for further investigation.

There have been more than 1700 wildlife-related reports from WA to the hotline since the first confirmed case on 19 June. Of these reports, 283 have been assessed for further investigation or testing based on the likelihood of disease risk.

To date, a total of 117 negative test results have been recorded across the State.

The risk to human health remains low, but people are reminded to avoid handling the animals, record their observations by photo or video and report to the EAD hotline on 1800 675 888.

More information is available on the Australian Government's Bird flu (Avian influenza) website.

The logistics of following up each prioritized hotline report of dead birds are both extensive and time consuming:

• Physically collecting and preserving carcasses (assuming they haven't been degraded by exposure or predation), often from remote regions. 

• Preliminary tests are run by local/state agricultural institutes to quickly confirm the presence the H5 subtype 

• Followed by packaging and sending biological samples to the only national testing laboratory (CSIRO Australian Centre for Disease Preparedness (ACDP) in Geelong, Victoria)

• Upon arrival, confirmation (and full sequencing) can take several days, assuming the sample had not degraded too badly. 

All of which helps to explains why it can take a week or longer to get confirmation on a suspected case.

While I've only seen aggregate totals posted by WA, it is apparent that the number of daily reports to their hotline far exceeds their ability to collect and test samples.  

 Graphic generated by Gemini

Over the past 12 days the number of tested samples has risen from 63 to 125 (avg 5/day), while the number of hotline reports has grown by 900 (avg 75/day).  Even if we limit it to prioritized reports, that number has averaged 13.75/day. 

Although testing has increased over the past 12 days, the number of new reports of sick or dead birds far outpaces those gains. 

 Graphic generated by Gemini

None of this is a criticism of Australia's response, only an acknowledgment of the enormity of the problem facing them. No surveillance and testing program can hope to capture more than a fraction of the HPAI activity in birds or animals in the wild. 

What testing can do is give us an idea as to the spread, intensity, and host range of HPAI H5 across the continent. And sequencing can alert us to any reassortments or significant changes to the virus over time.

While the absolute number of confirmed detections remains small (n=14) - and we've seen no reports of outbreaks in poultry or mammalian wildlife - the trends are nevertheless concerning.  

Respiratory Illness Low In The U.S., But Taiwan & Hong Kong Report Increased COVID Activity

 
Credit CDC

#19,246

Reassuringly, in their latest update (July 10th), the CDC is reporting very low respiratory illness in the United States right now.

What to know

• As of July 10, 2026, the amount of acute respiratory illness causing people to seek health care is very low. 

• RSV activity is very low in most areas of the country. Emergency department visits and hospitalizations for RSV are low but remain highest among infants and children younger than 4 years old. 

• COVID-19 activity is low and stable nationally but is beginning to increase from low in a few areas of the country. 

• Seasonal influenza activity is low. 

• Parainfluenza (PIV), a respiratory virus that can cause illnesses such as croup, is elevated nationally. Rhinovirus/enterovirus (RV/EV), which often cause cold-like respiratory illness, are also elevated nationally but is going down. Whooping cough (pertussis) is still circulating.

But, as mentioned above, some states are showing signs of increasing COVID activity, as depicted in the following CDC map.

While we've yet to see a summer surge in COVID this year in the United States, the virus continues to circulate - and evolve - around the globe, and some places are reporting increased activity. 

The most recent update from Hong Kong indicates COVID cases are rising:

Meanwhile, Taiwan's CDC issued the following (translated) statement today (July  14th).

As the COVID-19 pandemic continues to escalate, the public is urged to get vaccinated; those at risk of severe illness should seek medical attention immediately if they experience suspected symptoms.

 

 Release Date: 2026-07-14

The Centers for Disease Control (CDC) stated today (July 14th) that the domestic COVID-19 epidemic continues to escalate. To protect their own health and the health of others, the CDC urges the public to take self-prevention measures and get vaccinated against COVID-19 this season. It is recommended to wear masks when entering and exiting medical care facilities and in crowded places where proper social distancing cannot be maintained or ventilation is poor. If fever or respiratory symptoms occur, it is recommended to stay home and avoid unnecessary outings. Individuals with severe risk factors should seek medical attention as soon as possible if they experience suspected symptoms. A doctor can assess and conduct a rapid test, or they can use a commercially available home rapid test. A doctor can also assess and prescribe antiviral drugs for those with severe risk factors who test positive for COVID-19, reducing the risk of serious complications or death after infection.

The CDC stated that the domestic COVID-19 epidemic continues to rise. In the 27th week (July 5th-July 11th), there were 2,811 outpatient and emergency room visits for COVID-19, an increase of 34.4% compared to the previous week. Last week (July 7th-July 13th), there were 17 new local cases of severe COVID-19 complications, with no new local deaths. Since October 2025, a total of 136 local cases of severe COVID-19 complications have been reported, with 18 deaths. The majority of severe cases were among those aged 65 and above (72.1%) and those with a history of chronic diseases (83.8%). 94.9% of these cases were not vaccinated this season.

Globally, the COVID-19 positivity rate has recently increased, showing an upward trend in all regions except the Eastern Mediterranean region. Neighboring countries/regions such as China, Hong Kong, Japan, South Korea, and Singapore are also experiencing rising cases. Currently, the predominant circulating strain globally is NB.1.8.1, followed by JN.1 and XFG.

The Centers for Disease Control (CDC) indicates that as of July 12, 2026, approximately 1.732 million COVID-19 vaccinations have been administered this season. The vaccination rates among those aged 65 and above are 20.97% for the first dose and 0.51% for the second dose. International research has found that receiving the current season's COVID-19 vaccine provides additional protection on top of existing immunity.

Vaccination with the current season's COVID-19 vaccine can reduce the risk of visiting the emergency room or emergency outpatient clinic due to COVID-19 by approximately 48%–50%, and reduce the risk of hospitalization by approximately 53%–55%. This demonstrates that COVID-19 vaccination effectively reduces the severity of the disease and the medical burden caused by COVID-19, and has a significant protective effect in preventing severe illness and hospitalization.

The Taiwan Centers for Disease Control (CDC) urges that, as the majority of severe local COVID-19 cases in Taiwan are still among the elderly aged 65 and above and those with a history of chronic diseases, and most of them have not yet received the current season's COVID-19 vaccine, the CDC urges high-risk individuals, such as those aged 65 and above, who have not yet been vaccinated or have received their first dose at least 6 months ago, to get vaccinated as soon as possible to enhance their immune protection and reduce the risk of severe illness and hospitalization.

(Continue . . .)

 

Whether we get a significant summer surge in COVID remains to be seen, but the recent extended lull is no guarantee that futures outbreaks will not occur.  The CDC adds:

Season Outlook

CDC has observed a trend of declining COVID-19 hospitalizations nationally over time. However, it remains possible that there could be larger increases this summer, particularly if a variant that the immune system no longer recognizes becomes more common .

Scenario modeling indicates that regions which did not experience a substantial level of COVID-19 activity during the most recent winter months (South and West) are expected to experience increases in COVID-19 activity in the summer months. Read more: 2026 COVID-19 Summer Outlook | CFA: Qualitative Assessments | CDC

Which is why I've recently (May) gotten a COVID booster shot to hopefully boost my protection through the summer. 

WHO: Bangladesh Reports 3rd H5N1 Human Infection for 2026

#19,245

In their latest Influenza at the human-animal interface Summary and risk assessment (from 13 June to 7 July 2026) - published over the weekend - the WHO has announced a 3rd H5N1 case in a Bangladeshi child in the past 6 months. 

• Last April, we saw a fatal case reported from the Chattogram Division, in a child who fell ill on January 22nd, was hospitalized on January 28th, and who died on February 1st.  The H5N1 infection was only determined posthumously, via lab analysis on Feb 7th. 

• In early June we learned of a 2nd case, a child from Sylhet Division who was hospitalized on March 28th with a clinical diagnosis of measles with bronchopneumonia. The child was discharged on March 31st, but delayed testing by the IEDCR only revealed a positive H5N1 result on April 20th. 

Today, we have another report which - once again - was only fully diagnosed belatedly, and this time the child was only seen as an outpatient.  As with the last case, this case also hails from Sylhet Division. 

Avian influenza viruses in humans
A(H5), Bangladesh

On 15 June 2026, Bangladesh notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in Bangladesh in a child from Sylhet Division. The case was detected notified through the National Influenza Surveillance, Bangladesh (NISB) platform as an influenza like-illness (ILI) case.

The patient developed respiratory symptoms on 17 May 2026, received outpatient healthcare on 20 May. A clinical sample was collected that day and was received by the Institute of Epidemiology, Disease Control and Research (IEDCR) on 4 June as part of routine surveillance. 

The sample tested positive for influenza A(H5) virus by real-time reverse transcription polymerase chain reaction (RT-PCR) on 11 June. The patient is now in good health and reported no travel history and no history of exposure to poultry.

However, poultry deaths were reported in the area surrounding the patient’s residence. The outbreak investigation team identified and followed close and possible contacts. Samples from some of the close contacts as well as animal and environmental samples were collected for testing for influenza. All contacts remained asymptomatic and all samples tested negative for influenza.

This is the third laboratory-confirmed human case of avian influenza A(H5) reported in Bangladesh in 2026, and the 15th human case of avian influenza A(H5) reported to WHO from Bangladesh since 2008, including two fatal cases, one reported in 2013 and one in 2026

        (Continue . . . )

Sadly, this is a pattern we see far too often, and not just in Bangladesh.  Delayed diagnosis not only endangers the patient's health, it risks unknowingly exposing others to the virus, and delays greatly reduce the effectiveness contact tracing or testing of others who may have been exposed. 

We've seen numerous examples (see here, here, here, and here) of delayed diagnosis of novel flu in hospitalized patients, even here in the United States and in Europe (see H9N2 in Italy). 

Admittedly, novel flu can often present with atypical signs and symptoms, or may be mild or even asymptomatic, and not justify hospitalization or comprehensive testing (which may not even be available in some parts of the world). 

Additionally, standard throat swabs sometimes don't yield a positive result, and viral shedding can fluctuate over the course of infection, making false negatives not uncommon. 

Recognizing the problem, in 2024 the ECDC issued guidance for member nations on Enhanced Influenza Surveillance to Detect Avian Influenza Virus Infections in the EU/EEA During the Inter-Seasonal Period.

In that summary, the ECDC pointed out:

Sentinel surveillance systems are important for the monitoring of respiratory viruses in the EU/EEA, but these systems are not designed and are not sufficiently sensitive to identify a newly emerging virus such as avian influenza in the general population early enough for the purpose of implementing control measures in a timely way.

In January 2025 we saw a CDC HAN: Accelerated Subtyping of Influenza A in Hospitalized Patients, which urged immediate, and more thorough subtype testing of suspected flu cases.  

Since these are recommendations, and not mandates, it isn't clear how fine a net we are casting at the local level (see Idaho Health HAN: Consider Avian Influenza A (H5N1) in Patients with Dairy Cattle or Poultry Exposure).

Today's WHO report also summarizes 2 recent H9N2 cases (see chart below), and a novel H3N2v case from Brazil.

Influenza A(H3N2)v, Brazil

On 25 June 2026, Brazil notified PAHO/WHO of a laboratory-confirmed human infection with an influenza A(H3N2)v virus detected in a child in Santa Catarina state. The patient had symptom onset on 12 June 2026 and due to worsening respiratory symptoms, healthcare was sought on 16 June.

The patient was referred for hospital admission with a diagnosis of Severe Acute Respiratory Infection (SARI). Upon admission, an antigen test confirmed influenza A and the patient was placed in a private respiratory isolation room and antiviral treatment was initiated.

The patient was discharged on 19 June.

A nasopharyngeal swab sample was collected on 16 June and sent to the State public health laboratory for real-time RT-PCR. On 18 June, a swine-origin influenza H3 variant was suspected, and the sample was sent to the Laboratory of Respiratory Viruses, Exanthems, Enteroviruses, and Viral Emergencies (LVRE) at the Oswaldo Cruz Institute (Fiocruz/Rio de Janeiro) on 19 June.

Analyses confirmed the presence of an influenza A(H3N2)v virus via molecular testing and genomic sequencing. An investigation by the state and municipality epidemiological surveillance team found that all contacts were asymptomatic before, during and after the child’s illness.

The child's grandfather worked at a swine nursery housing approximately 5,000 animals, though he noted that sanitary barriers were in place. The child frequently visited the grandfather's home and had contact with him several days a week. This is the first human A(H3N2)v infection detected in the Brazil in 2026 and the first case reportedi n the state of Santa Catarina.

In this case, a novel H3 flu virus was suspected in the child after 2 days in the hospital, but was not confirmed until sometime after the patient was discharged (date not explicitly stated). 

It takes both planning - and certain amount of luck - to detect novel flu cases in the community, as confirmed cases only represent the very tip of the surveillance and reporting pyramid.  

While there is no evidence that HPAI H5 is spreading efficiently from human-to-human right now, the evidence suggests that it is spilling over into humans more often than we know.  

And even if there is some (as yet, unknown) species barrier that prevents H5 from ever becoming a pandemic, there are plenty of other viruses out there following similar paths. 

Eventually, one of them will get lucky. It's only a matter of time. 

Updated CDC Surveillance Numbers on Multi-State Cyclosporiasis Outbreak

CDC Surveillance Updated Jul 10th - 843 Confirmed cases

 #19,244

Ten days ago, in Cyclosporiasis Reports: CDC & Michigan DOH, we looked at early reports of a multi-state outbreak of cyclosporiasis, with the CDC reporting 145 cases acquired in the United States between May 1st and June 15th.

At the same time - and not included in the CDC's count - Michigan was reporting an additional 170 cyclosporiasis infections over the previous 9 days.

While fairly common in developing tropical, or sub-tropical countries, Cyclosporiasis – a parasite infection usually acquired through consuming food or water contaminated with Cyclospora cayetanensis - is relatively rare in the United States.

Although it still likely underrepresents the full burden of this outbreak, the CDC's latest update lists 843 confirmed cases, but acknowledges > 1,500 additional reports are under investigation. 

Surveillance of Cyclosporiasis

For Public Health
July 10, 2026

Key points

• CDC is aware that states are likely to report higher case counts of cyclosporiasis than reflected in CDC data and is working closely with states to update numbers as additional cases are confirmed. Since May 1, 2026, CDC has received reports of 843 confirmed domestic cases of cyclosporiasis and is aware of more than 1,500 cases that require further analysis to confirm the illness as domestically acquired cyclosporiasis. So far this year, multiple states have reported an increase in cases in the last two weeks compared to the same period in 2025.

• State and federal partners are working together to investigate several outbreaks of cyclosporiasis. Investigations to identify source(s) of illness are ongoing.

• Cyclosporiasis is a gastrointestinal disease caused by the microscopic parasite Cyclospora.

• On a regular basis, CDC reports all laboratory-confirmed cases that are received from states. State data may include both probable and confirmed cases, which in turn is likely to reflect a higher case count than the CDC surveillance data because initial case reports have not yet been reported to CDC. CDC does not report probable cases.

Current situation

As of July 9, 2026, 843 cases were reported in people who acquired cyclosporiasis in the United States. Cases were reported by 31 states. These people became sick after eating food in the United States and did not report any travel during the 14 days before they got sick.

Sick people ranged in age from 5 to 88 years, with a median age of 44, and 59% were female. The median illness onset date was June 18, 2026 (range: May 1 – July 5). Of 843 people with information available, 86 were hospitalized. No deaths have been reported.

Multiple jurisdictions have reported an increase of cases in the last two weeks compared to the same period in 2025. We assume a 6-week reporting lag between illness onset and case reporting to CDC; therefore, we anticipate that case counts will continue to rise as data are received.

CDC teams are working diligently to collect, analyze, and provide data at the national level. State health departments may have more timely information about the situation in their jurisdictions.

Local, state, and federal (CDC, FDA) public health authorities are investigating several clusters of cases in more than one state. The numbers reported on this page reflect a total surveillance count of cases across the United States, including clusters of cases currently under traceback investigation by FDA and cases that have not been linked to a common source. Investigations to identify potential sources are ongoing.

In order to help prevent infection, the CDC recommends:

Prevention tips

People can take the following food and vegetable handling recommendations to prevent foodborne illness related to fresh produce:

Wash

• Wash hands with soap and water before and after handling or preparing raw fruits and vegetables.

Prepare

• Wash all fruits and vegetables thoroughly under running water before eating, cutting, or cooking.
• Fruits and vegetables that are labeled "prewashed" do not need to be washed again at home.
• Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.
• Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.

Store

• Refrigerate cut, peeled, or cooked fruits and vegetables as soon as possible (within two hours).