H5N1 infection was fatal to six ferrets after ocular inoculation with the virus, according to a study today in Emerging Infectious Diseases.

The virus used in the experiment was A 2.3.4.4b, a highly pathogenic avian influenza A(H5N1) virus isolated from a human patient in Chile in 2023.

The ferrets were inoculated with both low and high doses of the virus via the ocular route. All ferrets inoculated with a high dose of virus had detectable infectious virus in nasal wash, the authors said, and the magnitude and frequency of viral titers in these specimens was reduced, but still present, in animals inoculated with a low dose.

"Our finding that a clade 2.3.4.4b H5N1 virus isolated from a human can exhibit a virulent and transmissible phenotype after nontraditional inoculation, even with a low dose of inoculum, underscores the public health threat posed by those IAVs [influenza A viruses]," the authors said. 

Our finding that a clade 2.3.4.4b H5N1 virus isolated from a human can exhibit a virulent and transmissible phenotype after nontraditional inoculation.

Low and high doses of virus infected animals 

Late last week, a study showed the current strain of H5N1 infecting US dairy cattle was fatal to ferrets. The strain used in that study came from a Texas dairy farmworker who was sickened with the virus. 

So far, three agricultural workers in the United States have been infected with the virus during ongoing farm outbreaks, all with mild illness. The first two workers reported eye infections. 

"Considering the myriad ways humans may be exposed to IAVs, our study supports the need to consider nontraditional inoculation modalities in risk assessment activities and supports consideration of using eye protection in potentially contaminated environments," the authors concluded. 

The Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) yesterday announced that lactating dairy cows must be tested for influenza A before movement to fairs and exhibits to prevent the spready of highly pathogenic H5N1 avian flu in cattle. So far, no H5N1 outbreaks have been reported in Wisconsin, but the virus has been detected in 12 states, including in neighboring Michigan, Minnesota, and Iowa. 

The testing measure takes effect on June 19, and samples must be collected no more than 7 days before movement to exhibitions. The order will remain in effect until 60 days after the last H5N1 detection in dairy herds in the United States.

More detections in US cattle, poultry, and wild birds

In other developments, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has reported 4 more H5N1 outbreaks in dairy herds, 3 from Idaho and 1 from Iowa, raising its confirmed outbreak total to 94.

Also, APHIS reported one more outbreak in poultry, which involves a backyard facility that houses 30 birds in Idaho's Jerome County. The group also reported more than 80 more H5N1 detections in wild birds, which included agency-harvested birds such as sparrows and starlings in Michigan and Idaho counties that have experienced outbreaks in dairy herds. Also, both captive birds and those found dead tested positive in Massachusetts.

Following Cuba's health ministry recent announcement of Oropouche virus cases, the World Health Organization (WHO) yesterday provided more details, including that the outbreak is the country's first involving the insect-borne virus. 

So far, 74 cases have been confirmed, 54 in Santiago de Cuba province and 20 in Cienfuegos province. The cases were found during enhanced surveillance following a rise in febrile illnesses. Illness onsets ranged from May 2 to May 23, with cases peaking during the week ending May 24. The most common symptoms were fever, low-back pain, headache, loss of appetite, vomiting, weakness, joint pain, and eye pain.

Slightly more than half of the patients were male, and the median age was 34 years. All patients showed signs of recovery at day 3 or 4 of their illnesses. So far, no severe or fatal cases have been reported. Oropouche virus is transmitted primarily through the bite of the Culicoides paraensis midge. 

Cuban population highly susceptible

The WHO said since Cuba is experiencing Oropouche virus infections for the first time and the country's population is highly susceptible, contributing to a risk of more cases. The agency also noted a risk of international spread, given that Cuba is a tourist destination and that the midge that carries the virus is widely distributed in the Americas.

Earlier this spring, the WHO's Pan American Health Organization warned of Oropouche virus rises in some Americas countries, with cases already reported in Brazil, Bolivia, Colombia, and Peru.

Infection with COVID-19 may offer protection against other, less severe endemic coronaviruses (eCOVs) that are often behind the common cold, according to a study today in Science Translational Medicine. COVID vaccines, however, don't appear to afford similar protection. 

Three coronaviruses can cause severe and fatal disease in humans: MERS-CoV, SARS, and SARS-CoV-2. But four eCOVs typically cause symptomatic, mild respiratory illnesses, accounting for 15% to 30% of "common colds."

The study was based on polymerase chain reaction test results from a retrospective cohort of 4,935 people who presented for clinical evaluation for respiratory illness from November 2020 to October 2021 at Boston Medical Center. 

Half the risk of symptomatic colds 

Participants were grouped into three categories: previous COVID-19 infection (501 participants), previous COVID-19 vaccine but no known infection (1,565), and no SARS-CoV-2 antigen exposures (no prior infection or vaccination; 2,869). 

"Incidence of symptomatic eCoV infection was significantly lower in those with prior SARS-CoV-2 infection and no vaccination (2 of 275, 0.7%) as compared with the individuals who had been deemed fully vaccinated but had no known prior SARS-CoV-2 infection (44 of 1,463, 3.0%)," the authors wrote. 

Incidence of symptomatic eCoV infection was significantly lower in those with prior SARS-CoV-2 infection and no vaccination

Previous COVID-19 infection was associated with an almost 50% reduced risk of a future symptomatic eCoV during the follow-up period of more than 120 days [hazard ratio 0.48, 95% confidence interval 0.21 to 1.1).

"Our observations have important implications for future pan-CoV vaccines and other disease prevention strategies," the authors concluded.

Patients who received one or more COVID-19 vaccine doses after acute coronary syndrome (ACS) had similar rates of all-cause death, heart attack, stroke, urgent coronary revascularization, major cardiovascular events, and hospitalization for chest pain, heart failure, and respiratory infections as their unvaccinated peers, according to a secondary analysis of a randomized clinical trial.

The research was published in JAMA Network Open.

No reduction in MACE

An international team led by researchers from Hospital Israelita Albert Einstein in Sao Paulo, Brazil, analyzed results from the Vaccination Against Influenza to Prevent Cardiovascular Events After Acute Coronary Syndromes trial. 

The trial evaluated the effectiveness of the influenza vaccine post-ACS from July 2019 to November 2020, while the secondary analysis compared the rate of cardiopulmonary events in patients who received at least one dose of COVID-19 vaccine in Brazil with that of unvaccinated participants. Patients were not randomized to the COVID vaccine in the secondary analysis.

In this secondary analysis of a randomized clinical trial, patients who received at least 1 COVID-19 vaccine dose after ACS had similar rates of the primary composite end point and MACE compared with unvaccinated patients.

Of 1,801 patients (median age, 56.7 years; 30.3% women), 16.2% had a history of heart attack, and 35.7% smoked. In total, 1,665 patients did not have cardiopulmonary events in the first 90 days, of whom 50.2% had received at least one COVID-19 vaccine dose. Most (63.9%) received at least one Oxford/AstraZeneca dose during follow-up.

In the 90-day event-free follow-up analysis of unvaccinated individuals, the rate of all-cause death, heart attack, stroke, urgent coronary revascularization, major cardiovascular events, and hospitalization for chest pain, heart failure, and respiratory infections per 100 patient-years was 9.37, versus 4.81 for vaccinated patients (adjusted hazard ratio [aHR], 0.41). 

Vaccination didn't significantly lower the rate of MACE (aHR, 0.32), all-cause death (aHR, 0.29), or cardiovascular death (aHR, 0.42). 

"In this secondary analysis of a randomized clinical trial, patients who received at least 1 COVID-19 vaccine dose after ACS had similar rates of the primary composite end point and MACE compared with unvaccinated patients," the researchers wrote. "However, retrospective studies have demonstrated a short-term reduction in MACE risk after COVID-19 vaccination."